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Synthesis, IR spectral studies and quantum-chemical calculations on 1,2-dihydronaphto[1,2-e]oxazine-3-thiones and 3,4-dihydrobenzo[e][1,3]oxazine-2-thione
Journal of Molecular Structure 830 (2007) 116–125 www.elsevier.com/locate/molstruc
Synthesis, IR spectral studies and quantum-chemical calculations on 1,2-dihydronaphto[1,2-e]oxazine-3-thiones and 3,4-dihydrobenzo[e][1,3]oxazine-2-thione Hikmet Agirbas a,¤, Seda Sagdinc b, Fatma Kandemirli a, Dilek Ozturk a a
Department of Chemistry, Kocaeli University, 41300 Izmit, Turkey b Department of Physics, Kocaeli University, 41300 Izmit, Turkey
Received 1 March 2006; received in revised form 28 June 2006; accepted 5 July 2006 Available online 22 August 2006
Abstract 2-Hydroxy-1-naphthaldehyde (1) was reacted with substituted anilines to aVord 1-(substituted phenyliminomethyl)naphthalen)-2ols (2). The reduction of these imines by NaBH4 gave 1-((substituted phenylaminomethyl)naphthalen)-2-ols (3) which were cyclized with thiophosgene to give corresponding 2-substituted phenyl-1,2-dihydronaphto[1,2-e]oxazine-3-thiones (4). 3-p-Tolyl-3,4dihydrobenzo[e][1,3]oxazine-2-thione (8) was also obtained by the same way. The structures of these new compounds were determined by 1H NMR, IR spectroscopic data and elemental analyses. AM1, PM3 and ab initio (at Hartree–Fock level with 3-21G basis set) methods were used to study the molecular geometry of the compounds. A complete infrared spectral analysis of the oxazines has been performed in this paper. Observed frequencies of the molecules were compared with calculated normal mode analysis which was carried out on the basis of RHF/3-21G method. Assignments of vibrational bands (in the range of 1760–400 cm¡1) have been performed by taking into account the results of the ab initio vibrational analysis. The mechanism of the cyclization reaction between (3a) and thiophosgene was studied by the semi-empirical AM1 and ab initio (RHF) calculations. © 2006 Elsevier B.V. All rights reserved. Keywords: Oxazine; Thiophosgene; IR spectra; MO calculations
1. Introduction Disease caused by Mycobacterium avium and Mycobacterium intracellulare are rare in the human population, but they are fatal. Therefore , the search for compounds which are active against these atypical stains is one of the primary goals of today’s medicinal chemistry. 3-Aryl-2H-1,3-benzoxazine-2,4(3H)-diones(dithiones) exhibited in vitro activity against Mycobacterium tuberculosis, M. kansasii and M. avium comparable to that of izoniazid (INH) [1,2]. Replacement of the oxo group by a thioxo group gave rise to an
*
Corresponding author. E-mail address: [email protected] (H. Agirbas).
0022-2860/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.molstruc.2006.07.010
increase of the activity against M. tuberculosis and M. kansasii. Our ongoing research is the synthesis and the structural studies of biological active Wve- and sixmembered heterocyclic compounds containing O, N and S atoms such as 3,4-disubstituted 1,2,4-oxa(thia) diazole-5-ones(thiones) [3–5] and 4-substituted 2,3-1Hbenzoxa(thia)zine-1-thiones(ones) [6]. Since the 1,3-benzoxazine derivatives show potential antibacterial activities [1,2] we have decided to synthesize new 1,3-oxazine derivatives by a new reaction route and study their structural properties. Oxazine derivatives also have potential applications in photochemical studies. Photolysis of 1,3oxazine-2-thiones give -thiolactones [7]. Naphthooxazines show photochromic properties [8,9]. Photochemical hydrogen abstraction from N-acyltetrahydro-1,3-oxazine-
H. Agirbas et al. / Journal of Molecular Structure 830 (2007) 116–125
H
O
OH
H2C
X
O
OH
OH
H2N
CSCl2
NaBH4
(2)
(1)
S
N
NH
N C
C
X
X
X
H
117
(4)
(3)
X
4a 4b
H CH3 CH3
CH3 CHO
CH
p-Toluidine
N
N H
NaBH4
N
CSCl 2
OH
(5)
CH3
H2 C
OH
(6)
OH
(7)
O
S
(8)
Scheme 1. Synthesis of compounds 4a, 4b and 8.
2-thiones [10] and triplet–triplet energy transfer between benzophenone and an oxazine dye co-adsorbed on the surface of microcrystalline cellulose have also been studied [11]. Ab initio quantum mechanical calculations are widely used methods for simulating IR spectra of the molecules. Such simulations are indispensable tools to perform normal coordinate analysis. Modern vibrational spectroscopy would be unimaginable without involving them. In this study, we report the assignments of complete IR spectra of compounds 4a, 4b and 8 supported by ab initio (RHF) calculations of all fundamental vibrations. We also report here the semi-empirical AM1 and ab initio (RHF) calculations of the cyclization reaction of 1-(phenylaminomethyl)naphthalen-2-ol (3a) with Cl2CBS. 2. Synthesis The synthesis of the title compounds was straightforward as illustrated in Scheme 1. 2-Hydroxy-1-naphthaldehyde (1) was reacted with substituted anilines to aVord the imines (2). Then the imines were reduced by NaBH4 to give 1-((substituted phenylaminomethyl)naphthalen)-2ols (3). These were cyclized with thiophosgene in the presence of pyridine to the corresponding 2-substituted phenyl-1,2-dihydronaphto[1,2-e]oxazine-3-thiones (4). Same reaction was carried out with salicylaldehyde and ptoluidine. After the cyclization of compound 7 with CSCl2, 3-p-tolyl-3,4-dihydrobenzo[e]oxazine-2-thione (8)
was obtained. The structures of compounds 4a, 4b and 8 were conWrmed by elemental analyses and by IR, 1H NMR and mass spectral methods. 3. Experimental The FTIR spectra were recorded using Shimadzu 8201 spectrometer with KBr technique, in the region 4000–400 cm¡1 that was calibrated by polystyrene. Melting points were determined on Electrothermal 9200 apparatus and are uncorrected. 1H NMR spectra were recorded on Bruker DPX-400 (400 MHz) High Performance Digital FT-NMR Spectrometer using CDCl3 with Me4Si as an internal standard. Elemental analyses were performed on Carlo Erba-1106 instrument. Mass spectra were run at 70 eV on VCZAP SpEC instrument. Silica Gel (Fluka or Merck) were used for column chromatography. SchiV bases (2) (Scheme 1) were synthesized according to the literature [12]. A band for the azomethine group was observed in IR spectrum at about 1620 cm¡1. For the reduction of SchiV bases with NaBH4 , compounds 2 were dissolved in 1:1 ratio in methanol and dioxan. NaBH4 was added to the stirred solution until the yellow color of the bases were disappeared. Cold water was added to the solution to precipitate the compounds. The precipitates were recrytallized from methanol to obtained compounds 3. Absorption bands for OH and NH groups were observed at 3360 cm¡1 and 3250 cm¡1, respectively.
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Table 1 Geometrical parameters of 8, 4b and 4a, calculated by ab initio (RHF) 3-21G Bond length (Å) 8
4b
4a
C(15)–C(16) C(14)–C(25) C(15)–C(14) C(14)–C(13) C(12)–C(13) C(11)–C(16) C(11)–C(12) C(10)–S(17) O(9)–C(10) C(11)–N(8) C(10)–N(8) C(7)–N(8) C(5)–C(6) O(9)–C(5) C(4)–C(7) C(4)–C(5) C(4)–C(3) C(2)–C(6) C(2)–C(1) C(3)–C(1)
1.68(2) 1.85 1.69 1.69 1.69 1.68 1.68 2.09 1.65 1.76 1.62 1.81 1.65 1.69 1.84 1.71 1.64 1.73 1.72 1.74
1.69(2) C(14)–C(15)–C(16) C(15)–C(14)–C(25) 1.69 C(13)–C(14)–C(25) 1.69 C(15)–C(14)–C(13) 1.69 C(14)–C(13)–C(12) 1.68 C(15)–C(16)–C(11) 1.68 C(11)–C(12)–C(13) 2.09 C(12)–C(11)–C(16) 1.65 C(16)–C(11)–N(8) 1.76 C(12)–C(11)–N(8) 1.62 C(11)–N(8)–C(10) 1.81 C(11)–N(8)–C(7) 1.65 C(10)–N(8)–C(7) 1.69 O(9)–C(10)–S(17) 1.84 S(17)–C(10)–N(8) 1.71 O(9)–C(10)–N(8) 1.64 C(10)–O(9)–C(5) 1.73 C(2)–C(6)–C(5) 1.72 C(4)–C(7)–N(8) 1.74 O(9)–C(5)–C(6) C(4)–C(5)–C(6) O(9)–C(5)–C(4) C(5)–C(4)–C(7) C(3)–C(4)–C(7) C(5)–C(4)–C(3) C(4)–C(3)–C(1) C(1)–C(2)–C(6) C(2)–C(1)–C(3)
1.68(2) 1.85 1.69 1.69 1.69 1.68 1.68 2.09 1.65 1.76 1.62 1.81 1.68 1.69 1.84 1.69 1.69 1.68 1.69 1.68
Bond angles (°)
Dihedral angles (°)
8
4b
4a
120.85 (2) 120.31 121.05 118.62 120.82 119.72 119.75 120.24 119.83 119.83 121.04 113.19 125.73 116.99 126.14 116.86 124.73 118.85 112.34 117.29 122.00 120.71 119.09 122.04 118.86 120.22 120.16 119.91
120.86(2) 120.34 121.27 118.59 120.85 119.74 119.73 120.22 119.68 120.02 121.09 113.19 125.72 117.10 128.60 118.48 124.55 120.81 112.40 115.66 118.97 121.53 119.12 121.55 122.81 119.33 119.35 118.72
120.06(2) C(14)–C(15)–C(16)–C(11) C(16)–C(15)–C(14)–C(13) C(15)–C(14)–C(13)–C(12) 120.00 C(25)–C(14)–C(13)–C(12) 120.06 C(11)–C(12)–C(13)–C(14) 119.57 N(8)–C(11)–C(16)–C(15) 119.58 C(12)–C(11)–C(16)–C(15) 120.72 N(8)–C(11)–C(12)–C(13) 119.60 C(16)–C(11)–C(12)–C(13) 119.57 C(5)–O(9)–C(10)–N(8) 121.13 C(5)–O(9)–C(10)–S(17) 113.03 C(12)–C(11)–N(8)–C(7) 125.85 C(12)–C(11)–N(8)–C(10) 117.19 C(16)–C(11)–N(8)–C(7) 126.23 C(16)–C(11)–N(8)–C(10) 116.59 O(9)–C(10)–N(8)–C(7) 124.51 O(9)–C(10)–N(8)–C(11) 119.35 S(17)–C(10)–N(8)–C(7) 112.36 S(17)–C(10)–N(8)–C(11) 115.63 C(4)–C(7)–N(8)–C(10) 118.99 C(4)–C(7)–N(8)–C(11) 121.59 C(4)–C(5)–C(6)–C(2) 119.10 O(9)–C(5)–C(6)–C(2) 121.56 C(10)–O(9)–C(5)–C(4) 122.78 C(10)–O(9)–C(5)–C(6) 119.34 C(3)–C(4)–C(7)–N(8) 119.35 C(5)–C(4)–C(7)–N(8) 118.71 C(3)–C(4)–C(5)–C(6) C(7)–C(4)–C(5)–C(6) C(3)–C(4)–C(5)–O(9) C(7)–C(4)–C(5)–O(9) C(5)–C(4)–C(3)–C(1) C(7)–C(4)–C(3)–C(1) C(1)–C(2)–C(6)–C(5) C(6)–C(2)–C(1)–C(3) C(4)–C(3)–C(1)–C(2)
3.1. Synthetic procedures 3.1.1. Synthesis of 2-phenyl-1,2-dihydronaphto[1,2-e]oxazine3-thione (4a) (general procedure) 1-(Phenylamino)methylnaphthalen-2-ol (3a) (2 mmol, 0.5 g) was dissolved 60 ml of CH2Cl2. Pyridine (4 mmol, 0.32 g) was added to the solution. Then, solution was cooled with ice–salt mixture and thiophosgene (2 mmol, 0.23 g) in CH2Cl2 (10 ml) was added dropwise. The reaction mixture was stirred overnight at room temperature. To separate the salt, water was added to the solution. Organic layer was taken and dried with anhydrous Na2SO4. The solvent was evaporated under vacuo. The residual oily matter was subjected to Xash column chromatography (eluent, ethyl acetate–petroleum ether, 1:3) and crystallized from THF:petroleum ether (3:1) to give 4a (0.25 g, 42%). Mp: 176–177 °C. Anal. Calcd for C18H13NOS: C,74.2; H, 4.5; N, 4.8%. Found: C, 73.93; H, 4.37; N, 4.8%. m/z 291 (100%, M+). Selected IR data (cm¡1): D 1190 (CBS). 1H NMR (CDCl 3 , ppm): D 5.1 (s, 2H, CH2); 7.2–7.5 (m, aromatic 6H); 7.8 (m, aromatic 5H).
8
4b
0.09(2) 0.14 ¡0.23 178.14 0.07 ¡176.59 ¡0.25 176.51 0.17 ¡4.51 175.44 ¡85.79 92.06 90.59 ¡91.59 ¡2.01 ¡179.64 177.96 0.42 7.27 ¡175.03 0.02 179.84 4.99 ¡174.83 174.28 ¡6.43 0.26 ¡179.06 ¡179.56 1.13 ¡0.33 178.97 ¡0.23 0.15 0.13
¡0.19(2) ¡0.09 0.15 179.91 ¡0.15 ¡176.71 ¡0.06 176.75 0.11 ¡1.06 178.89 ¡88.21 91.66 88.45 ¡91.68 ¡0.87 179.27 179.19 ¡0.67 2.07 ¡178.05 0.08 ¡179.97 1.55 ¡178.42 178.56 ¡1.50 0.06 179.88 179.86 ¡0.09 ¡0.18 ¡179.90 ¡0.10 ¡0.02 0.16
4a 0.20(2) ¡0.11 0.11 ¡0.19 ¡176.42 ¡0.29 176.42 0.28 ¡0.15 179.84 ¡87.99 91.91 88.18 ¡91.91 ¡0.09 ¡179.49 179.9 0.02 0.26 ¡179.84 ¡0.01 179.99 0.19 ¡179.79 179.79 ¡0.20 0.01 179.99 ¡179.99 0.01 ¡0.02 ¡179.99 ¡0.01 0.01 0.01
3.1.2. 2-p-Tolyl-1,2-dihydronaphto[1,2-e]oxazine-3-thione (4b) The compound was recrystallized from THF–petroleum ether (3:1); yield: 64%, mp: 185–186 °C. Anal. Calcd for C19H15NOS: C, 74.8; H, 4.9; N, 4.6%. Found: C, 74.09; H, 4.81; N, 4.26. Selected IR data (cm¡1): D 1184 (CBS). 1H NMR (CDCl3, ppm): D 2.4 (s, 3H, CH3); 5.1 (s, 2H, CH2); 7.3–7.8 (m, aromatic 10H). 3.1.3. 3-p-Tolyl-3,4-dihydrobenzo[e][1,3]oxazine-2-thione (8) The compound was recrystallized from THF–petroleum ether (5:1); yield: 61%, mp: 123–124 °C. Anal. Calcd for C15H13NOS: C, 70.6; H, 5.1; N, 5.5%. Found: C, 70.15; H, 5.15; N, 5.26. m/z: 255 (75%, M+). Selected IR data (cm¡1): D 1190 (CBS). 1H NMR (CDCl3, ppm) D 2.33 (s, 3H, CH3); 4.72 (s, 2H , CH2); 7.0–7.29 (m, aromatic 8H). 3.2. Method of calculation Theoretical calculations were performed with the HyperChem 7.5 program [13]. Geometry optimizations
H. Agirbas et al. / Journal of Molecular Structure 830 (2007) 116–125
119
Fig. 1. A model of the ab initio (RHF) optimized lowest-energy conformation of compounds 4a, 4b and 8 with the labelled atoms.
were used to Wnd the coordinates of molecular structures that represent a potential energy minimum. For HyperChem, the algorithm used is the Polak–Ribiere algorithm, and the termination condition is the RMS gradient of 0.1 kcal/mol. The lowest energy conformation, dipole moments, and energies are calculated at PM3, AM1 semi empirical methods and ab initio method (at both Hartree–Fock (RHF) and the Moller–Plesset seconder perturbation (MP2) levels of theory with 3-21G basis set). The selected charges of molecules were calculated by the ab initio (RHF) 3-21G basis set. To determine the conformational energy proWles of 4b, energy values of AM1, PM3 and the ab initio (RHF) 3-21G basis set were calculated as a func-
tions of the torsion angles (C(10)–N(8)–C(11)–C(16)) from 0 to 360° varied every 20° keeping the other torsional angle constant. The standard convergence criteria were used. The harmonic frequencies of molecules were also computed following ab initio 3-21G basis set. The assignment of the calculated wavenumbers is aided by the animation option of the same program, which gives a visual presentation of the shape of the vibrational modes. The electronic structures of the reactants (3a + Cl2CBS), their transition states, intermediate states and Wnal product 4a of the reaction were investigated on the base of AM1 method. Calculations for the reaction were performed with the GAUSSIAN 03 computational package program [14].
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H. Agirbas et al. / Journal of Molecular Structure 830 (2007) 116–125
Table 2 Calculated values of dipole moment (D), heat of formation (kcal/mol) and energy (kcal/mol) for (8), (4a) and (4b) PM3
AM1
Ab initio(RHF) 3-21G
MP2
Compound (8) Dipole moment 6.0 5.3 7.5 Energy ¡60363.3 ¡65011.9 ¡688097.9 Heat of formation 49.4 55.0
7.6 ¡688097.8
Compound (4a) Dipole moment 6.5 5.6 7.7 Energy ¡68543.9 ¡73855.8 ¡758990.1 Heat of formation 76.8 82.2
7.9 ¡758990.9
Compound (4b) Dipole moment 6.4 5.6 7.6 Energy ¡71996.7 ¡77450.5 ¡783350.6 Heat of formation 67.1 74.3
7.8 ¡783351.5
Table 3 Charges of C, N, O, S atoms of (4a), (4b) and (8) calculated by ab initio (RHF) 3-21G basis sets Atom No.
Fig. 3. FT-IR spectrum of compound 4a which shows the wave numbers that listed in Table 3.
Charges
C1 C2 C3 C4 C5 C6 C7 N8 O9 C10 C11 C12 C13 C14 C15 C16 S17 C25
4a
4b
8
¡0.090 ¡0.091 ¡0.192 ¡0.117 0.405 ¡0.199 ¡0.116 ¡0.948 ¡0.737 0.435 0.299 ¡0.209 ¡0.194 ¡0.232 ¡0.234 ¡0.208 ¡0.017 ¡0.194
¡0.090 ¡0.091 ¡0.193 ¡0.114 0.404 ¡0.198 ¡0.124 ¡0.949 ¡0.733 0.433 0.290 ¡0.208 ¡0.227 ¡0.066 ¡0.230 ¡0.188 ¡0.017 ¡0.586
¡0.23 ¡0.23 ¡0.22 ¡0.14 0.40 ¡0.23 ¡0.08 ¡0.95 ¡0.74 0.44 0.29 ¡0.23 ¡0.22 ¡0.06 ¡0.22 ¡0.19 ¡0.02 ¡0.58
Fig. 4. FT-IR spectrum of compound 4b which shows the wave numbers that listed in Table 3.
4. Results and discussion
Relative Energy (kcal/mol)
4.1. Geometric parameters 40 35 30 25 20 15 10 5 0 0
40
80
120
160
200
240
280
320
360
Torsion angles AM1
PM3
3-21G
Fig. 2. The curves of potential energies against torsion angles (varying every 10°) of C(10)–N(8)–C(11)–C(16) of 4b performed by AM1, PM3 and ab initio (RHF) 3-21G methods.
Optimized molecular structure parameters of the molecules, calculated by ab initio (RHF) 3-21G basis set are summarized in Table 1. The calculated structures of 4a, 4b and 8 is shown in Fig. 1. The optimized molecular geometries were obtained without symmetry constraints. The harmonic frequency calculations showed that the molecular geometries of the molecules correspond to the minimum energy structures. Computed dipole moment is a measure of the asymmetry in the molecular charge distribution and is given as a vector in three dimensions. The values of dipole moments and energies for 8, 4b and 4a were also calculated. The numerical (by four methods) values are listed in Table 2. According to AM1, PM3, ab initio (RHF) 3-21G and MP2 calculation methods, the energies have increasing tendency
H. Agirbas et al. / Journal of Molecular Structure 830 (2007) 116–125
Fig. 5. FT-IR spectrum of compound 8 which shows the wave numbers that listed in Table 3.
in the same order in each method. The order is 4b > 4a > 8. The values of dipole moment, calculated by AM1 method shows increasing tendency in the series given above. According to the data obtained by PM3, ab initio (RHF) 321 G and MP2, the order is 4a > 4b > 8. In Table 3, the atomic charges of C, O, N and S atoms of the molecules are given. The O9, N8, S17 and C7 atoms exhibit a substantial negative charge, which are the donor atoms. C10 atom exhibit a positive charge, which is an acceptor atom. 4.2. Conformational analysis In order to deWne conformational Xexibility of (4b), AM1, PM3 and ab initio (RHF) 3-21G calculations were carried out by rotating torsion angle of C(10)–N(8)– C(11)–C(16). The angle was varied every 10°. The results are illustrated in Fig. 2. The zero point calculations for each point in the curve show that the higher relative energy of the conformer corresponds to the lower zero point energy. The scans of the torsion angle at AM1, PM3 and ab initio (RHF)/3-21G levels allowed us to select two energy minima. The minima predicted by three methods coincide: AM1, PM3 and RHF/3-21G methods gave the minima at 70° and 250°; 90° and 270°; 80° and 270°, respectively. 4.3. Vibrational analysis The experimental (shown in Figs. 3–5) and calculated (by ab initio (RHF)/3-21G method) wavenumbers (in the range of 1760–400 cm¡1) of molecules 4a, 4b and 8 are given in Table 4. Because of both asymmetry and large size of the system, many vibrations are diYcult to describe, in particular those involving the coupled movement of several parts of groups. Some vibrations identiWed in the solid phase experimental
121
spectra could not be identiWed in the simulated counterparts and therefore, have been omitted. The diVerences between the calculated and experimental frequencies are due to anharmonicity, intermolecular interactions, an approximate treatment of electron correlation eVects and the limited basis set. When the calculated vibrational wavenumbers were compared with experimentally observed values, correlation coeYcient for 4a, 4b and 8 were found 0.9952, 0.996 and 0.9945, respectively (Fig. 6). Comparing to the molecules, certain changes of calculated and experimental bands of aliphatic, aromatic, thione, oxa atom and aza group can be noticed. The bands which characterize aromatic properties of benzene derivatives mainly occur within the range of 1640–1430 cm¡1 [(C–C)ar bands] and 1180–1030 cm¡1 [(C–H) bands]. In this study, these bands are observed in this range. But these bands shift to lower order wavenumbers as 4a > 4b > 8. The observed ring bands of 4b and 4a at 1402–1404 cm¡1 and at 1221– 1225 cm¡1, respectively, are absent in the IR spectra of 8 since the molecule does not carry naphto group. All the three compounds exhibit a strong thiocarbonyl (CBS) absorbtion in the region of 1184–1190 cm¡1. This is in agreement with the reported value [15] of 1150 § 70 cm¡1. According to the ab initio calculations, this band is assigned in the region of 1289–1297 cm¡1 for these compounds. 4.4. Computational methodology Since experimental results were insuYcient to explain the mechanism of the reactions, quantum chemical calculations were used for this aim. To study the mechanism of the reaction between 1-(phenylaminomethyl)naphtalen-2ol (3a) and CSCl2, quantum chemical calculations were carried out with AM1 method with full geometry optimisation for reactants, intermediates and Wnal products. Vibrational analysis was performed for transition states and one negative imaginary frequencies were found for every transition states. A transition state is a Wrst order saddle point on a potential energy surface (PES). The vibrational spectrum of a transition state is characterized by one imaginary frequency (implying a negative force constant), which means that in one direction in nuclear conWguration space the energy has a maximum, while in all other (orthogonal) directions. The quantum chemical results of the mechanism enabled us to suggest that reaction of 1-(phenylaminomethyl) naphtalen-2ol with CSCl2 proceeded through four transition states and three intermediates. A substantial role in the analysis of the paths of reactions belongs to the interaction of frontier HOMO (LUMO) orbitals of reactants. The calculations have shown that in the reacting system HOMO is represented by the atoms N13, C15, C17 belonging to 1-(phenylaminomethyl) naphtalen-2-ol while LUMO includes the atom C25, with the greatest values of their coeYcients. The localization of the frontier orbitals on the reacting centre forces the energy levels of the orbitals to approach each other. There
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Table 4 The experimental (FT-IR) and calculated (by ab initio (RHF) 3-21G basis sets) wavenumbers (in cm¡1) of (4a), (4b) and (8) Assignments
4aO
4bO
8O
4aC
4bC
8C
(ring) (CBC) (ring) (ring) (C–N)+ s (CH2) (ring)+s (CH2) (ring) s (CH2) (C–N)+s(CH2) (ring) (CH) (C–N)+t(CH2) (C–N)+ (CH3) (C–O) +(ring) (CH) (CH) C–C+(CH3) (CH)+ (C–C) (SBC)+(C–O) r(CH3)+ring (CH) t(CH2) C–C (CH) C–N+(C–O) (CH) Skeletal (CH) (CH) (CH) Ring + r(CH3) Ring C–C C–C (C–H) (CBS)+ (ring) CH3+ring CC (ring) (C–H) (ring) (CCC) r(CH3)+ring SBC+ring
1701(vw) 1641(m) 1591(m) 1518(mw) 1493(vs) 1464(mw) 1450(w) 1440(w) 1429(m) 1404(mw) 1385(m) 1356(m) – 1319 (vs) 1273(s) 1255(w) – 1225(vs) 1190(vs) – 1140(mw) – 1070(w) 1057(m) 1028(w) 1001(mw) 966(mw) 941(w) 916(vw) 852(mw) – 815(s) 770(m) 740(s) – 694(s) – 615(vw) 586(m) 530(w) 513(mw) 465(vw) – 407(w)
1691(vw) 1635(m) 1589(w) 1508(m) 1487(s) 1462(mw) – – 1435(s) 1402(mw) 1380(mw) 1346(m) – 1325(vs) 1276(mw) 1263(mw) 1232(vs) 1221(vs) 1184(vs) 1166(vs) 1136(m) 1109(w) 1076(vw) 1057(mw) 1026(w) 1006(w) 951(w) – 866(w) – 826(mw) 818(m) 773(w) 745(m) 710(mw) – 662(vw) 623(vw) 583(m) 536(vw) 515(w) – – 415(vw)
1686(vw) 1628(mw) 1595(m) 1499(s) 1483(s) 1462(m) – – 1443(s) – 1377(vw) – 1337(vs) 1286(mw) – 1248(s) 1228(s) – 1190(vs) 1163(s) 1150(m) 1107(m) – 1049(mw) 1018(vw) – 954(mw) 939(vw) 866(w) 833(w) 824(m) – – 761(vs) 713(mw) – 664(w) 623(w) 575(m) – 507(w) 468(vw) 432(w) –
1753(3) 1672(68) 1669(52) 1659(40) 1592(180) 1511(53) 1501(52) 1434(62) 1420(666) 1400(2) 1398(66) 1364(526) – 1353(127) 1322(215) 1317(82) – 1302(104) 1290(30) – 1140(17) 1121(16) 1102(14) 1087(28) 1083(15) 1063(35) 1036 901(22) 881(5) 873(55) – 806(59) 762(10) 728(14) 707(2) 678(34) – 617(9) 552(25) – 544(11) 467(3) – 426(8)
1753(4) 1687(71) 1671(53) 1663(8) 1590(189) 1510(53) 1501(53) 1434(67) 1420(655) 1400(11) 1398(56) 1364(491) – 1353(148) 1333(69) 1319(226) 1305(62) 1297(37) 1289(77) 1212(10) 1143(9) 1134(8) 1102(27) 1086(28) 1065(38) 1036(21) 962(30) – 889(2) 873(55) 855(12) 817(14) 739(7) 721(9) 712(3) – 674(27) 619(17) 552(25) – 531(9) 471(3) – 423(3)
1746(3) 1686(62) 1678(40) 1666(90) 1603(223) 1463(222) – – 1424(445) – 1411(20) – 1388(570) 1382(93) 1350(19) 1318(47) 1306(71) – 1297(94) 1212(14) 1140(7) 1121(9) – 1090(20) – 1028(4) 976(18) 897(94) – 872(6) 852(14) – 739(7) 719(9) 705(11) – 679(18) 617 542(36) – 511 495(3) 476 393
, stretching; , in plane bending; , out of plane bending; t, twisting; r, rocking; . s, strong; m, medium; w, weak; vw, very weak; Superscript: O, observed; C, calculated.
1600
Comp. 4a CC=0,9952
1400 1200 1000 800 600 400 400
600
800 1000 1200 1400 1600 1800
Experimental Frequencies (cm-1)
1800 1600
Comp. 4b CC=0,996
1400 1200 1000 800 600 400 400
600
800 1000 1200 1400 1600 1800
Experimental Frequencies (cm-1 )
Calculated Frequencies (cm-1)
1800
2000
2000
Calculated Frequencies (cm-1)
Calculated Frequencies (cm-1)
2000
1800 1600
Comp.8 CC=0,9945
1400 1200 1000 800 600 400 400 600 800 1000 1200 1400 1600 1800 Experimental Frequencies (cm-1)
Fig. 6. Graphic correlation between the experimental and calculated wavenumbers obtained by ab initio (RHF) method for compounds 4a, 4b and 8.
H. Agirbas et al. / Journal of Molecular Structure 830 (2007) 116–125
123
Energy Kcalmol-1
60
HOMO of 1-(phenylaminomethyl) naphtalen-2-ol
50 40 30 20 10 0 3+CSCl2
TS1 I3 TS2 Reaction Coordinate
I2
Energy Kcalmol-1
60
LUMO of CSCl2
Fig. 7. HOMO orbitals of 1-(phenylaminomethyl)naphthalen-2-ol (3a) and LUMO orbitals of Cl2CBS.
50 40 30 20 10 0 I2a
through, the interaction of the orbitals increases. It may be suggested that it is precisely the HOMO–LUMO (Fig. 7) and their constituent atoms C25 and N13 interaction, which is the Wrst stage of the reaction (Fig. 8). Energy characteristics, geometries of the reacting centre and charge distribution on atoms of systems participating in the reaction are given in Tables 5 and 6. The atoms spatial arrangements in reactants, intermediates, transition states (TS) and product are shown in Figs. 8 and 9. As seen from the Fig. 8, the mechanism of the reaction may be divided into four stages. At the Wrst stage the N13 atom of 3a reacts with the atom C25 in Cl2CBS. As the reacting molecules (3a + Cl2CBS) is far from each other (C5–N8 D 2.300Å), the bond C25–N13 and the bond C25–Cl27 are 1.728Å and 1.542Å, respectively. In the Wrst intermediate the bond C25– N13 is formed via nucleophilic attack. In the TS1, C25–N13 is equal to 1.991Å and bonds C25–S28 and C25–Cl lengthen (C25–N13 D 1.586Å, C25–Cl D 1.756Å). Imaginary
14 13
frequency is ¡470.53 cm¡1. In TS1 structure, the atom N13 is in a tetrahedral state (the angles of C14–N13–H24, C9–N13– H24, C9–N13–C25 and C14–N13–C25 are 109.89°, 109.62°, 106.06°, 110.18°) and carbon atom C25 forms a trigonal pyramid (the angles of Cl26–C25–S28, Cl27–C25–S28, and Cl26–C25–N13 are 122.17°, 121.01° , 97.06°). The negative charge on the atom N13 changes from ¡0.251 ç to ¡0.178 ç for TS1 and to ¡0.003 ç for I1. The electron density transfers from the nitrogen atom to the carbon atom, that causes the intermediate state I1 stabilization. The system transition to the intermediate stateI2 happens under the full breakage of the bond C25,Cl27 and proton H12 transfer to the Cl27 atom. The system transition to the state I2 happens through the TS2 formation.
26 25
2
11
27
12
3a+CSCl2
TS1
I1
TS2
I2
Fig. 8. Models of AM1 optimized lowest-energy conformation of Cl2CBS, TS1, I1, TS2 and I2.
I2a
TS3
I3
4a
Fig. 10. The potential energy proWle for the formation of (4a). Each state was calculated by AM1 method.
28
9 1
TS3 I3 TS4 Reaction Coordinate
TS4
Fig. 9. Models of AM1 optimized lowest-energy conformation of I2a, TS3, I3, TS4 and 4a.
4a
124
H. Agirbas et al. / Journal of Molecular Structure 830 (2007) 116–125
Table 5 Geometric and electronic values of (3a + Cl2CBS), TS1, I1, TS2, I2 Atom no.
TS1
3a+CSCl2 AM1
Bond length (Å) N13–C9 C9–C3 N13–C14 C3–C2 C2–C1 C2–O11 O11–H12 N13–C25 C25–S28 C25–Cl27 Cl27–H24 Energy au (AM1) IRC (cm¡1) Mulliken charges N13 C9 C14 C3 C2 O11 H12 C25 S28 Cl27 H24 Cl26
RHF
1.459 1.502 1.430 1.391 1.420 1.379 0.968 2.300 1.542 1.728 2.793
1.464 1.526 1.391 1.363 1.406 1.385 0.964 3.000 1.610 1.802 4.000
0.08519225
¡0.251 ¡0.041 0.001 ¡0.132 0.076 ¡0.262 0.223 ¡0.055 0.039 ¡0.024 0.185 ¡0.005
AM1 1.464 1.495 1.435 1.391 1.419 1.380 0.968 1.991 1.586
I1 RHF 1.484 1.521 1.421 1.362 1.405 1.387 0.964 2.376 1.641 1.828 2.799
0.10646252 ¡470.53
¡0.922 ¡0.166 0.384 ¡0.081 0.407 ¡0.758 0.401 ¡0.734 0.385 0.162 0.365 0.150
¡0.178 ¡0.061 ¡0.030 ¡0.128 0.078 ¡0.269 0.228 0.035 ¡0.170 ¡0.064 0.205 ¡0.038
TS2
AM1 1.500 1.493 1.465 1.391 1.420 1.379 0.968 1.593 1.666 1.814 2.630
RHF 1.538 1.513 1.487 1.359 1.404 1.397 0.966 1.540 1.773 1.950 2.553
0.10601062
¡0.853 ¡0.199 0.316 ¡0.079 0.399 ¡0.762 0.404 ¡0.634 0.202 0.111 0.378 0.165
¡0.003 ¡0.078 ¡0.082 ¡0.136 0.085 ¡0.277 0.236 0.0805 ¡0.449 ¡0.127 0.233 ¡0.095
AM1
I2 RHF
1.494 1.496 1.456 1.392 1.421 1.374 0.968 1.506 1.557 2.418 1.690
1.56900 1.50244 1.49522 1.36067 1.40735 1.37769 0.96757 1.44533 1.63099 3.61281 1.83056
0.12760645 ¡464.06
¡0.865 ¡0.192 0.255 ¡0.093 0.386 ¡0.777 0.428 ¡0.417 ¡0.145 ¡0.073 0.493 0.034
¡0.107 ¡0.050 ¡0.056 ¡0.138 0.101 ¡0.248 0.235 0.017 ¡0.018 ¡0.577 0.353 ¡0.023
AM1
RHF
1.462 1.495 1.430 1.393 1.422 1.378 0.968 1.366 1.597 2.800 1.296
1.51569 1.50124 1.44950 1.36033 1.40964 1.37883 0.96397 1.30426 1.71865 2.80000 1.29452
0.05655122
¡0.906 ¡0.179 0.233 ¡0.124 0.416 ¡0.747 0.421 ¡0.325 0.314 ¡0.731 0.450 0.221
¡0.184 0.009 ¡0.016 ¡0.125 0.100 ¡0.251 0.223 0.044 ¡0.224 ¡0.210 0.207 ¡0.005
¡0.843 ¡0.150 0.277 ¡0.121 0.427 ¡0.754 0.404 ¡0.124 ¡0.049 ¡0.246 0.252 0.094
Table 6 Geometric and electronic values of I2a, TS3, I3, TS4 and 4a Atom no.
I2a AM1
Bond length (Å) N13–C9 C9–C3 N13–C14 C3–C2 C2–C1 C2–O11 O11–H12 N13–C24 C24–S26 C24–Cl25 Cl25–H12 S26–H12 Energy au (AM1) IRC (cm¡1) Mulliken charges N13 C9 C14 C3 C2 O11 H12 C24 S26 Cl25
1.457 1.499 1.428 1.391 1.422 1.376 0.969 1.371 1.577 1.746 5.452 4.447
TS3 RHF 1.485 1.526 1.456 1.359 1.414 1.396 0.968 1.313 1.673 1.890 2.560 3.699
0.09373601
¡0.217 ¡0.014 0.026 ¡0.132 0.098 ¡0.243 0.223 ¡0.030 ¡0.126 ¡0.126
AM1 1.458 1.503 1.432 1.386 1.415 1.384 1.052 1.420 1.707 1.769 3.395 1.997
I3 RHF 1.475 1.518 1.438 1.350 1.404 1.384 1.206 1.377 1.850 1.938 3.303 1.768
0.166622702 ¡1233.47
¡0.864 ¡0.1445 0.266 ¡0.045 0.338 ¡0.756 0.423 ¡0.119 0.116 ¡0.020
¡0.239 ¡0.006 0.024 ¡0.128 0.034 ¡0.237 0.322 0.187 ¡0.320 ¡0.033
TS4
AM1 1.462 1.499 1.436 1.384 1.422 1.385 2.670 1.454 1.799 1.799 3.899 1.322
RHF 1.485 1.519 1.44277 1.35511 1.40961 1.39159 2.66388 1.39647 1.85512 1.91964 3.04207 1.34916
0.10301279
¡0.863 ¡0.124 0.283 ¡0.060 0.436 ¡0.784 0.413 0.117 ¡0.096 ¡0.095
¡0.233 ¡0.024 ¡0.021 ¡0.162 0.069 ¡0.216 0.036 0.112 ¡0.096 ¡0.059
AM1 1.459 1.495 1.432 1.380 1.420 1.396 3.069 1.374 1.761 2.216 2.018 1.412
4a RHF 1.49820 1.51074 1.45165 1.34458 1.40130 1.40487 2.68647 1.29507 1.81795 2.70860 2.83277 1.34989
0.13039742 ¡996.91
¡0.820 ¡0.161 0.241 ¡0.067 0.398 ¡0.704 0.107 0.093 0.235 ¡0.043
¡0.232 0.015 0.015 ¡0.131 0.069 ¡0.126 0.187 0.245 ¡0.00 ¡0.53
AM1 1.453 1.493 1.431 1.379 1.422 1.388 3.064 1.366 1.598 3.300 1.304 2.294
RHF 1.490 1.507 1.446 1.344 1.406 1.392 3.069 1.321 1.736 3.300 1.311 2.450
0.08749549
¡0.919 ¡0.102 0.221 ¡0.079 0.405 ¡0.730 0.190 0.610 0.281 ¡0.845
¡0.241 0.022 0.031 ¡0.149 0.068 ¡0.140 0.215 0.160 ¡0.189 ¡0.234
¡0.954 ¡0.085 0.286 ¡0.098 0.399 ¡0.744 0.241 0.471 ¡0.052 ¡0.290
H. Agirbas et al. / Journal of Molecular Structure 830 (2007) 116–125
Imaginary frequency is ¡464.07 cm¡1. The negative charge on the atom N13 increases from ¡0.003 ç to ¡0.184 and the negative charge on the atom S28 decreases from ¡0.449 ç to ¡0.224 in this state This shows the bonds polarization. At the third stage, the transition state TS3 is being formed when the O11,C24 distance becomes equal to 1.674Å. This stage is a cyclization reaction resulting in the intermediate I3 formation. At the last stage full breakage of Cl25–C24 and proton H10 transfer to the Cl25 atom occur. According to the calculation carried out, the reaction between 3a and Cl2CBS passes through the four stages. At the Wrst stage, a molecule of 3a combines with Cl2CBS by nucleophilic addition. Wnal product 4a is obtained via 2 mole HCl elimination. For reagents 3a+Cl2CBS, the total of electronic energy is 0.08519225 a.u. (Fig. 10, energy given in kcal/mol). For intermediates I1, I2 and I3 the totals are equal to 0.262961 a.u., 0.05655122 a.u. and 0.10301279 a.u., respectively. The transition of 3a+Cl2CBS into I1, I2, I3 and Wnally, into 4a happens through transition states TS1, TS2, TS3 and TS4. The values of the activation barrier E for TS1, TS2, TS3 and TS4 are 0.10646252 a.u., 0.12760645 a.u., 0.166622702 a.u. and 0.13039742 a.u., respectively. Ab initio (RHF) 3-21G calculations were also carried out for the mechanistic study. The results were given in Tables 5 and 6. The bond lengths were found mainly similar with AM1 results, but mullican charges of some atoms diVer substantially. Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.molstruc. 2006.07.010.
125
References [1] K. Waisser, J. Gregor, L. Kubicova, V. Klimesova, J. Kunes, M. Machacek, J. Kaustova, Eur. J. Med. Chem. 35 (2000) 33. [2] K. Waisser, J. Gregor, H. Dostal, J. Kunes, L. Kubicova, V. Klimesova, J. Kaustova, Il Farmaco 56 (2001) 803. [3] H. Agirbas, A.G. Kaya, M. Aydogdu, Phosphorus Sulfur 149 (1999) 39. [4] H. Agirbas, A. Toker, J. Phys. Org. Chem. 14 (1) (2001) 58. [5] H. Agirbas, Y. Kara, Phosphorus Sulfur 179 (7) (2004) 1435. [6] H. Agirbas, S. Guner, Phosphorus Sulfur 161 (2000) 257. [7] M. Sakamoto, M. Takahashi, M. Yoshiaki, T. Fujita, S. Watanabe, H. Aoyama, J. Chem. Soc. Perkin 1 (20) (1994) 2983. [8] S. Minkovska, B. Jeliazkova, E. Borisova, L. Avramov, T. Deligeorgiev, J. Photochem. Photobiol. A. 163 (2004) 121. [9] S. Minkovska, K. Kolev, B. Jeliazkova, T. Deligeorgiev, Dyes Pigments 39 (1) (1998) 25. [10] M. Sakamoto, S. Watanabe, T. Fujita, H. Aoyama, J. Chem. Soc. Perkin 1 (10) (1991) 2541. [11] F. Wilkinson, P.A. Leicester, L.P.V. Ferreira, V.M.M.R. Freire, J. Photochem. Photobiol. 54 (4) (1991) 599. [12] A.I. Vogel, Pratical Organic Chmistry, Longman, London, 1972. [13] HyperChem 7.5 Release for Windows, Hypercube Inc., USA, 2002. [14] M.J.Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman, V.G. Zakrzewski, J.A. Montgomery, R.E.J. Jr. Stratmann, C. Burant, S. Dapprich, J.M. Millam, A.D. Daniels, K.N. Kudin, M.C. Strain, O. Farkas, J. Tomasi, V. Barone, M.Cossi, R. Cammi, B. Mennucci, C. Pomelli, C. Adamo, S. CliVord, J. Ochterski, G.A. Petersson, P.Y. Ayala, Q. Cui, K. Morokuma, D.K. Malick, A.D. Rabuck, K. Raghavachari, J.B. Foresman, J. Cioslowski, J.V. Ortiz, A.G. Baboul, B.B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. Gomperts, R.L. Martin, D.J. Fox, T. Keith, M.A. Al-Laham, C.Y. Peng, A. Nanayakkara, M.P. Challacombe, M.W. Gill, B. Johnson, W. Chen, M.W. Wong, J.L. Andres, C. Gonzalez, M. Head-Gordon, E.S. Replogle, J.A. Pople, Gaussian 98, Revision A.9, Gaussian Inc., Pittsburgh, PA, 1998. [15] M. Mazharuddin, G. Thyagarajan, Tetrahedron 25 (1969) 517.
Synthesis, IR spectral studies and quantum-chemical calculations on 1,2-dihydronaphto[1,2-e]oxazine-3-thiones and 3,4-dihydrobenzo[e][1,3]oxazine-2-thione Hikmet Agirbas a,¤, Seda Sagdinc b, Fatma Kandemirli a, Dilek Ozturk a a
Department of Chemistry, Kocaeli University, 41300 Izmit, Turkey b Department of Physics, Kocaeli University, 41300 Izmit, Turkey
Received 1 March 2006; received in revised form 28 June 2006; accepted 5 July 2006 Available online 22 August 2006
Abstract 2-Hydroxy-1-naphthaldehyde (1) was reacted with substituted anilines to aVord 1-(substituted phenyliminomethyl)naphthalen)-2ols (2). The reduction of these imines by NaBH4 gave 1-((substituted phenylaminomethyl)naphthalen)-2-ols (3) which were cyclized with thiophosgene to give corresponding 2-substituted phenyl-1,2-dihydronaphto[1,2-e]oxazine-3-thiones (4). 3-p-Tolyl-3,4dihydrobenzo[e][1,3]oxazine-2-thione (8) was also obtained by the same way. The structures of these new compounds were determined by 1H NMR, IR spectroscopic data and elemental analyses. AM1, PM3 and ab initio (at Hartree–Fock level with 3-21G basis set) methods were used to study the molecular geometry of the compounds. A complete infrared spectral analysis of the oxazines has been performed in this paper. Observed frequencies of the molecules were compared with calculated normal mode analysis which was carried out on the basis of RHF/3-21G method. Assignments of vibrational bands (in the range of 1760–400 cm¡1) have been performed by taking into account the results of the ab initio vibrational analysis. The mechanism of the cyclization reaction between (3a) and thiophosgene was studied by the semi-empirical AM1 and ab initio (RHF) calculations. © 2006 Elsevier B.V. All rights reserved. Keywords: Oxazine; Thiophosgene; IR spectra; MO calculations
1. Introduction Disease caused by Mycobacterium avium and Mycobacterium intracellulare are rare in the human population, but they are fatal. Therefore , the search for compounds which are active against these atypical stains is one of the primary goals of today’s medicinal chemistry. 3-Aryl-2H-1,3-benzoxazine-2,4(3H)-diones(dithiones) exhibited in vitro activity against Mycobacterium tuberculosis, M. kansasii and M. avium comparable to that of izoniazid (INH) [1,2]. Replacement of the oxo group by a thioxo group gave rise to an
*
Corresponding author. E-mail address: [email protected] (H. Agirbas).
0022-2860/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.molstruc.2006.07.010
increase of the activity against M. tuberculosis and M. kansasii. Our ongoing research is the synthesis and the structural studies of biological active Wve- and sixmembered heterocyclic compounds containing O, N and S atoms such as 3,4-disubstituted 1,2,4-oxa(thia) diazole-5-ones(thiones) [3–5] and 4-substituted 2,3-1Hbenzoxa(thia)zine-1-thiones(ones) [6]. Since the 1,3-benzoxazine derivatives show potential antibacterial activities [1,2] we have decided to synthesize new 1,3-oxazine derivatives by a new reaction route and study their structural properties. Oxazine derivatives also have potential applications in photochemical studies. Photolysis of 1,3oxazine-2-thiones give -thiolactones [7]. Naphthooxazines show photochromic properties [8,9]. Photochemical hydrogen abstraction from N-acyltetrahydro-1,3-oxazine-
H. Agirbas et al. / Journal of Molecular Structure 830 (2007) 116–125
H
O
OH
H2C
X
O
OH
OH
H2N
CSCl2
NaBH4
(2)
(1)
S
N
NH
N C
C
X
X
X
H
117
(4)
(3)
X
4a 4b
H CH3 CH3
CH3 CHO
CH
p-Toluidine
N
N H
NaBH4
N
CSCl 2
OH
(5)
CH3
H2 C
OH
(6)
OH
(7)
O
S
(8)
Scheme 1. Synthesis of compounds 4a, 4b and 8.
2-thiones [10] and triplet–triplet energy transfer between benzophenone and an oxazine dye co-adsorbed on the surface of microcrystalline cellulose have also been studied [11]. Ab initio quantum mechanical calculations are widely used methods for simulating IR spectra of the molecules. Such simulations are indispensable tools to perform normal coordinate analysis. Modern vibrational spectroscopy would be unimaginable without involving them. In this study, we report the assignments of complete IR spectra of compounds 4a, 4b and 8 supported by ab initio (RHF) calculations of all fundamental vibrations. We also report here the semi-empirical AM1 and ab initio (RHF) calculations of the cyclization reaction of 1-(phenylaminomethyl)naphthalen-2-ol (3a) with Cl2CBS. 2. Synthesis The synthesis of the title compounds was straightforward as illustrated in Scheme 1. 2-Hydroxy-1-naphthaldehyde (1) was reacted with substituted anilines to aVord the imines (2). Then the imines were reduced by NaBH4 to give 1-((substituted phenylaminomethyl)naphthalen)-2ols (3). These were cyclized with thiophosgene in the presence of pyridine to the corresponding 2-substituted phenyl-1,2-dihydronaphto[1,2-e]oxazine-3-thiones (4). Same reaction was carried out with salicylaldehyde and ptoluidine. After the cyclization of compound 7 with CSCl2, 3-p-tolyl-3,4-dihydrobenzo[e]oxazine-2-thione (8)
was obtained. The structures of compounds 4a, 4b and 8 were conWrmed by elemental analyses and by IR, 1H NMR and mass spectral methods. 3. Experimental The FTIR spectra were recorded using Shimadzu 8201 spectrometer with KBr technique, in the region 4000–400 cm¡1 that was calibrated by polystyrene. Melting points were determined on Electrothermal 9200 apparatus and are uncorrected. 1H NMR spectra were recorded on Bruker DPX-400 (400 MHz) High Performance Digital FT-NMR Spectrometer using CDCl3 with Me4Si as an internal standard. Elemental analyses were performed on Carlo Erba-1106 instrument. Mass spectra were run at 70 eV on VCZAP SpEC instrument. Silica Gel (Fluka or Merck) were used for column chromatography. SchiV bases (2) (Scheme 1) were synthesized according to the literature [12]. A band for the azomethine group was observed in IR spectrum at about 1620 cm¡1. For the reduction of SchiV bases with NaBH4 , compounds 2 were dissolved in 1:1 ratio in methanol and dioxan. NaBH4 was added to the stirred solution until the yellow color of the bases were disappeared. Cold water was added to the solution to precipitate the compounds. The precipitates were recrytallized from methanol to obtained compounds 3. Absorption bands for OH and NH groups were observed at 3360 cm¡1 and 3250 cm¡1, respectively.
118
H. Agirbas et al. / Journal of Molecular Structure 830 (2007) 116–125
Table 1 Geometrical parameters of 8, 4b and 4a, calculated by ab initio (RHF) 3-21G Bond length (Å) 8
4b
4a
C(15)–C(16) C(14)–C(25) C(15)–C(14) C(14)–C(13) C(12)–C(13) C(11)–C(16) C(11)–C(12) C(10)–S(17) O(9)–C(10) C(11)–N(8) C(10)–N(8) C(7)–N(8) C(5)–C(6) O(9)–C(5) C(4)–C(7) C(4)–C(5) C(4)–C(3) C(2)–C(6) C(2)–C(1) C(3)–C(1)
1.68(2) 1.85 1.69 1.69 1.69 1.68 1.68 2.09 1.65 1.76 1.62 1.81 1.65 1.69 1.84 1.71 1.64 1.73 1.72 1.74
1.69(2) C(14)–C(15)–C(16) C(15)–C(14)–C(25) 1.69 C(13)–C(14)–C(25) 1.69 C(15)–C(14)–C(13) 1.69 C(14)–C(13)–C(12) 1.68 C(15)–C(16)–C(11) 1.68 C(11)–C(12)–C(13) 2.09 C(12)–C(11)–C(16) 1.65 C(16)–C(11)–N(8) 1.76 C(12)–C(11)–N(8) 1.62 C(11)–N(8)–C(10) 1.81 C(11)–N(8)–C(7) 1.65 C(10)–N(8)–C(7) 1.69 O(9)–C(10)–S(17) 1.84 S(17)–C(10)–N(8) 1.71 O(9)–C(10)–N(8) 1.64 C(10)–O(9)–C(5) 1.73 C(2)–C(6)–C(5) 1.72 C(4)–C(7)–N(8) 1.74 O(9)–C(5)–C(6) C(4)–C(5)–C(6) O(9)–C(5)–C(4) C(5)–C(4)–C(7) C(3)–C(4)–C(7) C(5)–C(4)–C(3) C(4)–C(3)–C(1) C(1)–C(2)–C(6) C(2)–C(1)–C(3)
1.68(2) 1.85 1.69 1.69 1.69 1.68 1.68 2.09 1.65 1.76 1.62 1.81 1.68 1.69 1.84 1.69 1.69 1.68 1.69 1.68
Bond angles (°)
Dihedral angles (°)
8
4b
4a
120.85 (2) 120.31 121.05 118.62 120.82 119.72 119.75 120.24 119.83 119.83 121.04 113.19 125.73 116.99 126.14 116.86 124.73 118.85 112.34 117.29 122.00 120.71 119.09 122.04 118.86 120.22 120.16 119.91
120.86(2) 120.34 121.27 118.59 120.85 119.74 119.73 120.22 119.68 120.02 121.09 113.19 125.72 117.10 128.60 118.48 124.55 120.81 112.40 115.66 118.97 121.53 119.12 121.55 122.81 119.33 119.35 118.72
120.06(2) C(14)–C(15)–C(16)–C(11) C(16)–C(15)–C(14)–C(13) C(15)–C(14)–C(13)–C(12) 120.00 C(25)–C(14)–C(13)–C(12) 120.06 C(11)–C(12)–C(13)–C(14) 119.57 N(8)–C(11)–C(16)–C(15) 119.58 C(12)–C(11)–C(16)–C(15) 120.72 N(8)–C(11)–C(12)–C(13) 119.60 C(16)–C(11)–C(12)–C(13) 119.57 C(5)–O(9)–C(10)–N(8) 121.13 C(5)–O(9)–C(10)–S(17) 113.03 C(12)–C(11)–N(8)–C(7) 125.85 C(12)–C(11)–N(8)–C(10) 117.19 C(16)–C(11)–N(8)–C(7) 126.23 C(16)–C(11)–N(8)–C(10) 116.59 O(9)–C(10)–N(8)–C(7) 124.51 O(9)–C(10)–N(8)–C(11) 119.35 S(17)–C(10)–N(8)–C(7) 112.36 S(17)–C(10)–N(8)–C(11) 115.63 C(4)–C(7)–N(8)–C(10) 118.99 C(4)–C(7)–N(8)–C(11) 121.59 C(4)–C(5)–C(6)–C(2) 119.10 O(9)–C(5)–C(6)–C(2) 121.56 C(10)–O(9)–C(5)–C(4) 122.78 C(10)–O(9)–C(5)–C(6) 119.34 C(3)–C(4)–C(7)–N(8) 119.35 C(5)–C(4)–C(7)–N(8) 118.71 C(3)–C(4)–C(5)–C(6) C(7)–C(4)–C(5)–C(6) C(3)–C(4)–C(5)–O(9) C(7)–C(4)–C(5)–O(9) C(5)–C(4)–C(3)–C(1) C(7)–C(4)–C(3)–C(1) C(1)–C(2)–C(6)–C(5) C(6)–C(2)–C(1)–C(3) C(4)–C(3)–C(1)–C(2)
3.1. Synthetic procedures 3.1.1. Synthesis of 2-phenyl-1,2-dihydronaphto[1,2-e]oxazine3-thione (4a) (general procedure) 1-(Phenylamino)methylnaphthalen-2-ol (3a) (2 mmol, 0.5 g) was dissolved 60 ml of CH2Cl2. Pyridine (4 mmol, 0.32 g) was added to the solution. Then, solution was cooled with ice–salt mixture and thiophosgene (2 mmol, 0.23 g) in CH2Cl2 (10 ml) was added dropwise. The reaction mixture was stirred overnight at room temperature. To separate the salt, water was added to the solution. Organic layer was taken and dried with anhydrous Na2SO4. The solvent was evaporated under vacuo. The residual oily matter was subjected to Xash column chromatography (eluent, ethyl acetate–petroleum ether, 1:3) and crystallized from THF:petroleum ether (3:1) to give 4a (0.25 g, 42%). Mp: 176–177 °C. Anal. Calcd for C18H13NOS: C,74.2; H, 4.5; N, 4.8%. Found: C, 73.93; H, 4.37; N, 4.8%. m/z 291 (100%, M+). Selected IR data (cm¡1): D 1190 (CBS). 1H NMR (CDCl 3 , ppm): D 5.1 (s, 2H, CH2); 7.2–7.5 (m, aromatic 6H); 7.8 (m, aromatic 5H).
8
4b
0.09(2) 0.14 ¡0.23 178.14 0.07 ¡176.59 ¡0.25 176.51 0.17 ¡4.51 175.44 ¡85.79 92.06 90.59 ¡91.59 ¡2.01 ¡179.64 177.96 0.42 7.27 ¡175.03 0.02 179.84 4.99 ¡174.83 174.28 ¡6.43 0.26 ¡179.06 ¡179.56 1.13 ¡0.33 178.97 ¡0.23 0.15 0.13
¡0.19(2) ¡0.09 0.15 179.91 ¡0.15 ¡176.71 ¡0.06 176.75 0.11 ¡1.06 178.89 ¡88.21 91.66 88.45 ¡91.68 ¡0.87 179.27 179.19 ¡0.67 2.07 ¡178.05 0.08 ¡179.97 1.55 ¡178.42 178.56 ¡1.50 0.06 179.88 179.86 ¡0.09 ¡0.18 ¡179.90 ¡0.10 ¡0.02 0.16
4a 0.20(2) ¡0.11 0.11 ¡0.19 ¡176.42 ¡0.29 176.42 0.28 ¡0.15 179.84 ¡87.99 91.91 88.18 ¡91.91 ¡0.09 ¡179.49 179.9 0.02 0.26 ¡179.84 ¡0.01 179.99 0.19 ¡179.79 179.79 ¡0.20 0.01 179.99 ¡179.99 0.01 ¡0.02 ¡179.99 ¡0.01 0.01 0.01
3.1.2. 2-p-Tolyl-1,2-dihydronaphto[1,2-e]oxazine-3-thione (4b) The compound was recrystallized from THF–petroleum ether (3:1); yield: 64%, mp: 185–186 °C. Anal. Calcd for C19H15NOS: C, 74.8; H, 4.9; N, 4.6%. Found: C, 74.09; H, 4.81; N, 4.26. Selected IR data (cm¡1): D 1184 (CBS). 1H NMR (CDCl3, ppm): D 2.4 (s, 3H, CH3); 5.1 (s, 2H, CH2); 7.3–7.8 (m, aromatic 10H). 3.1.3. 3-p-Tolyl-3,4-dihydrobenzo[e][1,3]oxazine-2-thione (8) The compound was recrystallized from THF–petroleum ether (5:1); yield: 61%, mp: 123–124 °C. Anal. Calcd for C15H13NOS: C, 70.6; H, 5.1; N, 5.5%. Found: C, 70.15; H, 5.15; N, 5.26. m/z: 255 (75%, M+). Selected IR data (cm¡1): D 1190 (CBS). 1H NMR (CDCl3, ppm) D 2.33 (s, 3H, CH3); 4.72 (s, 2H , CH2); 7.0–7.29 (m, aromatic 8H). 3.2. Method of calculation Theoretical calculations were performed with the HyperChem 7.5 program [13]. Geometry optimizations
H. Agirbas et al. / Journal of Molecular Structure 830 (2007) 116–125
119
Fig. 1. A model of the ab initio (RHF) optimized lowest-energy conformation of compounds 4a, 4b and 8 with the labelled atoms.
were used to Wnd the coordinates of molecular structures that represent a potential energy minimum. For HyperChem, the algorithm used is the Polak–Ribiere algorithm, and the termination condition is the RMS gradient of 0.1 kcal/mol. The lowest energy conformation, dipole moments, and energies are calculated at PM3, AM1 semi empirical methods and ab initio method (at both Hartree–Fock (RHF) and the Moller–Plesset seconder perturbation (MP2) levels of theory with 3-21G basis set). The selected charges of molecules were calculated by the ab initio (RHF) 3-21G basis set. To determine the conformational energy proWles of 4b, energy values of AM1, PM3 and the ab initio (RHF) 3-21G basis set were calculated as a func-
tions of the torsion angles (C(10)–N(8)–C(11)–C(16)) from 0 to 360° varied every 20° keeping the other torsional angle constant. The standard convergence criteria were used. The harmonic frequencies of molecules were also computed following ab initio 3-21G basis set. The assignment of the calculated wavenumbers is aided by the animation option of the same program, which gives a visual presentation of the shape of the vibrational modes. The electronic structures of the reactants (3a + Cl2CBS), their transition states, intermediate states and Wnal product 4a of the reaction were investigated on the base of AM1 method. Calculations for the reaction were performed with the GAUSSIAN 03 computational package program [14].
120
H. Agirbas et al. / Journal of Molecular Structure 830 (2007) 116–125
Table 2 Calculated values of dipole moment (D), heat of formation (kcal/mol) and energy (kcal/mol) for (8), (4a) and (4b) PM3
AM1
Ab initio(RHF) 3-21G
MP2
Compound (8) Dipole moment 6.0 5.3 7.5 Energy ¡60363.3 ¡65011.9 ¡688097.9 Heat of formation 49.4 55.0
7.6 ¡688097.8
Compound (4a) Dipole moment 6.5 5.6 7.7 Energy ¡68543.9 ¡73855.8 ¡758990.1 Heat of formation 76.8 82.2
7.9 ¡758990.9
Compound (4b) Dipole moment 6.4 5.6 7.6 Energy ¡71996.7 ¡77450.5 ¡783350.6 Heat of formation 67.1 74.3
7.8 ¡783351.5
Table 3 Charges of C, N, O, S atoms of (4a), (4b) and (8) calculated by ab initio (RHF) 3-21G basis sets Atom No.
Fig. 3. FT-IR spectrum of compound 4a which shows the wave numbers that listed in Table 3.
Charges
C1 C2 C3 C4 C5 C6 C7 N8 O9 C10 C11 C12 C13 C14 C15 C16 S17 C25
4a
4b
8
¡0.090 ¡0.091 ¡0.192 ¡0.117 0.405 ¡0.199 ¡0.116 ¡0.948 ¡0.737 0.435 0.299 ¡0.209 ¡0.194 ¡0.232 ¡0.234 ¡0.208 ¡0.017 ¡0.194
¡0.090 ¡0.091 ¡0.193 ¡0.114 0.404 ¡0.198 ¡0.124 ¡0.949 ¡0.733 0.433 0.290 ¡0.208 ¡0.227 ¡0.066 ¡0.230 ¡0.188 ¡0.017 ¡0.586
¡0.23 ¡0.23 ¡0.22 ¡0.14 0.40 ¡0.23 ¡0.08 ¡0.95 ¡0.74 0.44 0.29 ¡0.23 ¡0.22 ¡0.06 ¡0.22 ¡0.19 ¡0.02 ¡0.58
Fig. 4. FT-IR spectrum of compound 4b which shows the wave numbers that listed in Table 3.
4. Results and discussion
Relative Energy (kcal/mol)
4.1. Geometric parameters 40 35 30 25 20 15 10 5 0 0
40
80
120
160
200
240
280
320
360
Torsion angles AM1
PM3
3-21G
Fig. 2. The curves of potential energies against torsion angles (varying every 10°) of C(10)–N(8)–C(11)–C(16) of 4b performed by AM1, PM3 and ab initio (RHF) 3-21G methods.
Optimized molecular structure parameters of the molecules, calculated by ab initio (RHF) 3-21G basis set are summarized in Table 1. The calculated structures of 4a, 4b and 8 is shown in Fig. 1. The optimized molecular geometries were obtained without symmetry constraints. The harmonic frequency calculations showed that the molecular geometries of the molecules correspond to the minimum energy structures. Computed dipole moment is a measure of the asymmetry in the molecular charge distribution and is given as a vector in three dimensions. The values of dipole moments and energies for 8, 4b and 4a were also calculated. The numerical (by four methods) values are listed in Table 2. According to AM1, PM3, ab initio (RHF) 3-21G and MP2 calculation methods, the energies have increasing tendency
H. Agirbas et al. / Journal of Molecular Structure 830 (2007) 116–125
Fig. 5. FT-IR spectrum of compound 8 which shows the wave numbers that listed in Table 3.
in the same order in each method. The order is 4b > 4a > 8. The values of dipole moment, calculated by AM1 method shows increasing tendency in the series given above. According to the data obtained by PM3, ab initio (RHF) 321 G and MP2, the order is 4a > 4b > 8. In Table 3, the atomic charges of C, O, N and S atoms of the molecules are given. The O9, N8, S17 and C7 atoms exhibit a substantial negative charge, which are the donor atoms. C10 atom exhibit a positive charge, which is an acceptor atom. 4.2. Conformational analysis In order to deWne conformational Xexibility of (4b), AM1, PM3 and ab initio (RHF) 3-21G calculations were carried out by rotating torsion angle of C(10)–N(8)– C(11)–C(16). The angle was varied every 10°. The results are illustrated in Fig. 2. The zero point calculations for each point in the curve show that the higher relative energy of the conformer corresponds to the lower zero point energy. The scans of the torsion angle at AM1, PM3 and ab initio (RHF)/3-21G levels allowed us to select two energy minima. The minima predicted by three methods coincide: AM1, PM3 and RHF/3-21G methods gave the minima at 70° and 250°; 90° and 270°; 80° and 270°, respectively. 4.3. Vibrational analysis The experimental (shown in Figs. 3–5) and calculated (by ab initio (RHF)/3-21G method) wavenumbers (in the range of 1760–400 cm¡1) of molecules 4a, 4b and 8 are given in Table 4. Because of both asymmetry and large size of the system, many vibrations are diYcult to describe, in particular those involving the coupled movement of several parts of groups. Some vibrations identiWed in the solid phase experimental
121
spectra could not be identiWed in the simulated counterparts and therefore, have been omitted. The diVerences between the calculated and experimental frequencies are due to anharmonicity, intermolecular interactions, an approximate treatment of electron correlation eVects and the limited basis set. When the calculated vibrational wavenumbers were compared with experimentally observed values, correlation coeYcient for 4a, 4b and 8 were found 0.9952, 0.996 and 0.9945, respectively (Fig. 6). Comparing to the molecules, certain changes of calculated and experimental bands of aliphatic, aromatic, thione, oxa atom and aza group can be noticed. The bands which characterize aromatic properties of benzene derivatives mainly occur within the range of 1640–1430 cm¡1 [(C–C)ar bands] and 1180–1030 cm¡1 [(C–H) bands]. In this study, these bands are observed in this range. But these bands shift to lower order wavenumbers as 4a > 4b > 8. The observed ring bands of 4b and 4a at 1402–1404 cm¡1 and at 1221– 1225 cm¡1, respectively, are absent in the IR spectra of 8 since the molecule does not carry naphto group. All the three compounds exhibit a strong thiocarbonyl (CBS) absorbtion in the region of 1184–1190 cm¡1. This is in agreement with the reported value [15] of 1150 § 70 cm¡1. According to the ab initio calculations, this band is assigned in the region of 1289–1297 cm¡1 for these compounds. 4.4. Computational methodology Since experimental results were insuYcient to explain the mechanism of the reactions, quantum chemical calculations were used for this aim. To study the mechanism of the reaction between 1-(phenylaminomethyl)naphtalen-2ol (3a) and CSCl2, quantum chemical calculations were carried out with AM1 method with full geometry optimisation for reactants, intermediates and Wnal products. Vibrational analysis was performed for transition states and one negative imaginary frequencies were found for every transition states. A transition state is a Wrst order saddle point on a potential energy surface (PES). The vibrational spectrum of a transition state is characterized by one imaginary frequency (implying a negative force constant), which means that in one direction in nuclear conWguration space the energy has a maximum, while in all other (orthogonal) directions. The quantum chemical results of the mechanism enabled us to suggest that reaction of 1-(phenylaminomethyl) naphtalen-2ol with CSCl2 proceeded through four transition states and three intermediates. A substantial role in the analysis of the paths of reactions belongs to the interaction of frontier HOMO (LUMO) orbitals of reactants. The calculations have shown that in the reacting system HOMO is represented by the atoms N13, C15, C17 belonging to 1-(phenylaminomethyl) naphtalen-2-ol while LUMO includes the atom C25, with the greatest values of their coeYcients. The localization of the frontier orbitals on the reacting centre forces the energy levels of the orbitals to approach each other. There
122
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Table 4 The experimental (FT-IR) and calculated (by ab initio (RHF) 3-21G basis sets) wavenumbers (in cm¡1) of (4a), (4b) and (8) Assignments
4aO
4bO
8O
4aC
4bC
8C
(ring) (CBC) (ring) (ring) (C–N)+ s (CH2) (ring)+s (CH2) (ring) s (CH2) (C–N)+s(CH2) (ring) (CH) (C–N)+t(CH2) (C–N)+ (CH3) (C–O) +(ring) (CH) (CH) C–C+(CH3) (CH)+ (C–C) (SBC)+(C–O) r(CH3)+ring (CH) t(CH2) C–C (CH) C–N+(C–O) (CH) Skeletal (CH) (CH) (CH) Ring + r(CH3) Ring C–C C–C (C–H) (CBS)+ (ring) CH3+ring CC (ring) (C–H) (ring) (CCC) r(CH3)+ring SBC+ring
1701(vw) 1641(m) 1591(m) 1518(mw) 1493(vs) 1464(mw) 1450(w) 1440(w) 1429(m) 1404(mw) 1385(m) 1356(m) – 1319 (vs) 1273(s) 1255(w) – 1225(vs) 1190(vs) – 1140(mw) – 1070(w) 1057(m) 1028(w) 1001(mw) 966(mw) 941(w) 916(vw) 852(mw) – 815(s) 770(m) 740(s) – 694(s) – 615(vw) 586(m) 530(w) 513(mw) 465(vw) – 407(w)
1691(vw) 1635(m) 1589(w) 1508(m) 1487(s) 1462(mw) – – 1435(s) 1402(mw) 1380(mw) 1346(m) – 1325(vs) 1276(mw) 1263(mw) 1232(vs) 1221(vs) 1184(vs) 1166(vs) 1136(m) 1109(w) 1076(vw) 1057(mw) 1026(w) 1006(w) 951(w) – 866(w) – 826(mw) 818(m) 773(w) 745(m) 710(mw) – 662(vw) 623(vw) 583(m) 536(vw) 515(w) – – 415(vw)
1686(vw) 1628(mw) 1595(m) 1499(s) 1483(s) 1462(m) – – 1443(s) – 1377(vw) – 1337(vs) 1286(mw) – 1248(s) 1228(s) – 1190(vs) 1163(s) 1150(m) 1107(m) – 1049(mw) 1018(vw) – 954(mw) 939(vw) 866(w) 833(w) 824(m) – – 761(vs) 713(mw) – 664(w) 623(w) 575(m) – 507(w) 468(vw) 432(w) –
1753(3) 1672(68) 1669(52) 1659(40) 1592(180) 1511(53) 1501(52) 1434(62) 1420(666) 1400(2) 1398(66) 1364(526) – 1353(127) 1322(215) 1317(82) – 1302(104) 1290(30) – 1140(17) 1121(16) 1102(14) 1087(28) 1083(15) 1063(35) 1036 901(22) 881(5) 873(55) – 806(59) 762(10) 728(14) 707(2) 678(34) – 617(9) 552(25) – 544(11) 467(3) – 426(8)
1753(4) 1687(71) 1671(53) 1663(8) 1590(189) 1510(53) 1501(53) 1434(67) 1420(655) 1400(11) 1398(56) 1364(491) – 1353(148) 1333(69) 1319(226) 1305(62) 1297(37) 1289(77) 1212(10) 1143(9) 1134(8) 1102(27) 1086(28) 1065(38) 1036(21) 962(30) – 889(2) 873(55) 855(12) 817(14) 739(7) 721(9) 712(3) – 674(27) 619(17) 552(25) – 531(9) 471(3) – 423(3)
1746(3) 1686(62) 1678(40) 1666(90) 1603(223) 1463(222) – – 1424(445) – 1411(20) – 1388(570) 1382(93) 1350(19) 1318(47) 1306(71) – 1297(94) 1212(14) 1140(7) 1121(9) – 1090(20) – 1028(4) 976(18) 897(94) – 872(6) 852(14) – 739(7) 719(9) 705(11) – 679(18) 617 542(36) – 511 495(3) 476 393
, stretching; , in plane bending; , out of plane bending; t, twisting; r, rocking; . s, strong; m, medium; w, weak; vw, very weak; Superscript: O, observed; C, calculated.
1600
Comp. 4a CC=0,9952
1400 1200 1000 800 600 400 400
600
800 1000 1200 1400 1600 1800
Experimental Frequencies (cm-1)
1800 1600
Comp. 4b CC=0,996
1400 1200 1000 800 600 400 400
600
800 1000 1200 1400 1600 1800
Experimental Frequencies (cm-1 )
Calculated Frequencies (cm-1)
1800
2000
2000
Calculated Frequencies (cm-1)
Calculated Frequencies (cm-1)
2000
1800 1600
Comp.8 CC=0,9945
1400 1200 1000 800 600 400 400 600 800 1000 1200 1400 1600 1800 Experimental Frequencies (cm-1)
Fig. 6. Graphic correlation between the experimental and calculated wavenumbers obtained by ab initio (RHF) method for compounds 4a, 4b and 8.
H. Agirbas et al. / Journal of Molecular Structure 830 (2007) 116–125
123
Energy Kcalmol-1
60
HOMO of 1-(phenylaminomethyl) naphtalen-2-ol
50 40 30 20 10 0 3+CSCl2
TS1 I3 TS2 Reaction Coordinate
I2
Energy Kcalmol-1
60
LUMO of CSCl2
Fig. 7. HOMO orbitals of 1-(phenylaminomethyl)naphthalen-2-ol (3a) and LUMO orbitals of Cl2CBS.
50 40 30 20 10 0 I2a
through, the interaction of the orbitals increases. It may be suggested that it is precisely the HOMO–LUMO (Fig. 7) and their constituent atoms C25 and N13 interaction, which is the Wrst stage of the reaction (Fig. 8). Energy characteristics, geometries of the reacting centre and charge distribution on atoms of systems participating in the reaction are given in Tables 5 and 6. The atoms spatial arrangements in reactants, intermediates, transition states (TS) and product are shown in Figs. 8 and 9. As seen from the Fig. 8, the mechanism of the reaction may be divided into four stages. At the Wrst stage the N13 atom of 3a reacts with the atom C25 in Cl2CBS. As the reacting molecules (3a + Cl2CBS) is far from each other (C5–N8 D 2.300Å), the bond C25–N13 and the bond C25–Cl27 are 1.728Å and 1.542Å, respectively. In the Wrst intermediate the bond C25– N13 is formed via nucleophilic attack. In the TS1, C25–N13 is equal to 1.991Å and bonds C25–S28 and C25–Cl lengthen (C25–N13 D 1.586Å, C25–Cl D 1.756Å). Imaginary
14 13
frequency is ¡470.53 cm¡1. In TS1 structure, the atom N13 is in a tetrahedral state (the angles of C14–N13–H24, C9–N13– H24, C9–N13–C25 and C14–N13–C25 are 109.89°, 109.62°, 106.06°, 110.18°) and carbon atom C25 forms a trigonal pyramid (the angles of Cl26–C25–S28, Cl27–C25–S28, and Cl26–C25–N13 are 122.17°, 121.01° , 97.06°). The negative charge on the atom N13 changes from ¡0.251 ç to ¡0.178 ç for TS1 and to ¡0.003 ç for I1. The electron density transfers from the nitrogen atom to the carbon atom, that causes the intermediate state I1 stabilization. The system transition to the intermediate stateI2 happens under the full breakage of the bond C25,Cl27 and proton H12 transfer to the Cl27 atom. The system transition to the state I2 happens through the TS2 formation.
26 25
2
11
27
12
3a+CSCl2
TS1
I1
TS2
I2
Fig. 8. Models of AM1 optimized lowest-energy conformation of Cl2CBS, TS1, I1, TS2 and I2.
I2a
TS3
I3
4a
Fig. 10. The potential energy proWle for the formation of (4a). Each state was calculated by AM1 method.
28
9 1
TS3 I3 TS4 Reaction Coordinate
TS4
Fig. 9. Models of AM1 optimized lowest-energy conformation of I2a, TS3, I3, TS4 and 4a.
4a
124
H. Agirbas et al. / Journal of Molecular Structure 830 (2007) 116–125
Table 5 Geometric and electronic values of (3a + Cl2CBS), TS1, I1, TS2, I2 Atom no.
TS1
3a+CSCl2 AM1
Bond length (Å) N13–C9 C9–C3 N13–C14 C3–C2 C2–C1 C2–O11 O11–H12 N13–C25 C25–S28 C25–Cl27 Cl27–H24 Energy au (AM1) IRC (cm¡1) Mulliken charges N13 C9 C14 C3 C2 O11 H12 C25 S28 Cl27 H24 Cl26
RHF
1.459 1.502 1.430 1.391 1.420 1.379 0.968 2.300 1.542 1.728 2.793
1.464 1.526 1.391 1.363 1.406 1.385 0.964 3.000 1.610 1.802 4.000
0.08519225
¡0.251 ¡0.041 0.001 ¡0.132 0.076 ¡0.262 0.223 ¡0.055 0.039 ¡0.024 0.185 ¡0.005
AM1 1.464 1.495 1.435 1.391 1.419 1.380 0.968 1.991 1.586
I1 RHF 1.484 1.521 1.421 1.362 1.405 1.387 0.964 2.376 1.641 1.828 2.799
0.10646252 ¡470.53
¡0.922 ¡0.166 0.384 ¡0.081 0.407 ¡0.758 0.401 ¡0.734 0.385 0.162 0.365 0.150
¡0.178 ¡0.061 ¡0.030 ¡0.128 0.078 ¡0.269 0.228 0.035 ¡0.170 ¡0.064 0.205 ¡0.038
TS2
AM1 1.500 1.493 1.465 1.391 1.420 1.379 0.968 1.593 1.666 1.814 2.630
RHF 1.538 1.513 1.487 1.359 1.404 1.397 0.966 1.540 1.773 1.950 2.553
0.10601062
¡0.853 ¡0.199 0.316 ¡0.079 0.399 ¡0.762 0.404 ¡0.634 0.202 0.111 0.378 0.165
¡0.003 ¡0.078 ¡0.082 ¡0.136 0.085 ¡0.277 0.236 0.0805 ¡0.449 ¡0.127 0.233 ¡0.095
AM1
I2 RHF
1.494 1.496 1.456 1.392 1.421 1.374 0.968 1.506 1.557 2.418 1.690
1.56900 1.50244 1.49522 1.36067 1.40735 1.37769 0.96757 1.44533 1.63099 3.61281 1.83056
0.12760645 ¡464.06
¡0.865 ¡0.192 0.255 ¡0.093 0.386 ¡0.777 0.428 ¡0.417 ¡0.145 ¡0.073 0.493 0.034
¡0.107 ¡0.050 ¡0.056 ¡0.138 0.101 ¡0.248 0.235 0.017 ¡0.018 ¡0.577 0.353 ¡0.023
AM1
RHF
1.462 1.495 1.430 1.393 1.422 1.378 0.968 1.366 1.597 2.800 1.296
1.51569 1.50124 1.44950 1.36033 1.40964 1.37883 0.96397 1.30426 1.71865 2.80000 1.29452
0.05655122
¡0.906 ¡0.179 0.233 ¡0.124 0.416 ¡0.747 0.421 ¡0.325 0.314 ¡0.731 0.450 0.221
¡0.184 0.009 ¡0.016 ¡0.125 0.100 ¡0.251 0.223 0.044 ¡0.224 ¡0.210 0.207 ¡0.005
¡0.843 ¡0.150 0.277 ¡0.121 0.427 ¡0.754 0.404 ¡0.124 ¡0.049 ¡0.246 0.252 0.094
Table 6 Geometric and electronic values of I2a, TS3, I3, TS4 and 4a Atom no.
I2a AM1
Bond length (Å) N13–C9 C9–C3 N13–C14 C3–C2 C2–C1 C2–O11 O11–H12 N13–C24 C24–S26 C24–Cl25 Cl25–H12 S26–H12 Energy au (AM1) IRC (cm¡1) Mulliken charges N13 C9 C14 C3 C2 O11 H12 C24 S26 Cl25
1.457 1.499 1.428 1.391 1.422 1.376 0.969 1.371 1.577 1.746 5.452 4.447
TS3 RHF 1.485 1.526 1.456 1.359 1.414 1.396 0.968 1.313 1.673 1.890 2.560 3.699
0.09373601
¡0.217 ¡0.014 0.026 ¡0.132 0.098 ¡0.243 0.223 ¡0.030 ¡0.126 ¡0.126
AM1 1.458 1.503 1.432 1.386 1.415 1.384 1.052 1.420 1.707 1.769 3.395 1.997
I3 RHF 1.475 1.518 1.438 1.350 1.404 1.384 1.206 1.377 1.850 1.938 3.303 1.768
0.166622702 ¡1233.47
¡0.864 ¡0.1445 0.266 ¡0.045 0.338 ¡0.756 0.423 ¡0.119 0.116 ¡0.020
¡0.239 ¡0.006 0.024 ¡0.128 0.034 ¡0.237 0.322 0.187 ¡0.320 ¡0.033
TS4
AM1 1.462 1.499 1.436 1.384 1.422 1.385 2.670 1.454 1.799 1.799 3.899 1.322
RHF 1.485 1.519 1.44277 1.35511 1.40961 1.39159 2.66388 1.39647 1.85512 1.91964 3.04207 1.34916
0.10301279
¡0.863 ¡0.124 0.283 ¡0.060 0.436 ¡0.784 0.413 0.117 ¡0.096 ¡0.095
¡0.233 ¡0.024 ¡0.021 ¡0.162 0.069 ¡0.216 0.036 0.112 ¡0.096 ¡0.059
AM1 1.459 1.495 1.432 1.380 1.420 1.396 3.069 1.374 1.761 2.216 2.018 1.412
4a RHF 1.49820 1.51074 1.45165 1.34458 1.40130 1.40487 2.68647 1.29507 1.81795 2.70860 2.83277 1.34989
0.13039742 ¡996.91
¡0.820 ¡0.161 0.241 ¡0.067 0.398 ¡0.704 0.107 0.093 0.235 ¡0.043
¡0.232 0.015 0.015 ¡0.131 0.069 ¡0.126 0.187 0.245 ¡0.00 ¡0.53
AM1 1.453 1.493 1.431 1.379 1.422 1.388 3.064 1.366 1.598 3.300 1.304 2.294
RHF 1.490 1.507 1.446 1.344 1.406 1.392 3.069 1.321 1.736 3.300 1.311 2.450
0.08749549
¡0.919 ¡0.102 0.221 ¡0.079 0.405 ¡0.730 0.190 0.610 0.281 ¡0.845
¡0.241 0.022 0.031 ¡0.149 0.068 ¡0.140 0.215 0.160 ¡0.189 ¡0.234
¡0.954 ¡0.085 0.286 ¡0.098 0.399 ¡0.744 0.241 0.471 ¡0.052 ¡0.290
H. Agirbas et al. / Journal of Molecular Structure 830 (2007) 116–125
Imaginary frequency is ¡464.07 cm¡1. The negative charge on the atom N13 increases from ¡0.003 ç to ¡0.184 and the negative charge on the atom S28 decreases from ¡0.449 ç to ¡0.224 in this state This shows the bonds polarization. At the third stage, the transition state TS3 is being formed when the O11,C24 distance becomes equal to 1.674Å. This stage is a cyclization reaction resulting in the intermediate I3 formation. At the last stage full breakage of Cl25–C24 and proton H10 transfer to the Cl25 atom occur. According to the calculation carried out, the reaction between 3a and Cl2CBS passes through the four stages. At the Wrst stage, a molecule of 3a combines with Cl2CBS by nucleophilic addition. Wnal product 4a is obtained via 2 mole HCl elimination. For reagents 3a+Cl2CBS, the total of electronic energy is 0.08519225 a.u. (Fig. 10, energy given in kcal/mol). For intermediates I1, I2 and I3 the totals are equal to 0.262961 a.u., 0.05655122 a.u. and 0.10301279 a.u., respectively. The transition of 3a+Cl2CBS into I1, I2, I3 and Wnally, into 4a happens through transition states TS1, TS2, TS3 and TS4. The values of the activation barrier E for TS1, TS2, TS3 and TS4 are 0.10646252 a.u., 0.12760645 a.u., 0.166622702 a.u. and 0.13039742 a.u., respectively. Ab initio (RHF) 3-21G calculations were also carried out for the mechanistic study. The results were given in Tables 5 and 6. The bond lengths were found mainly similar with AM1 results, but mullican charges of some atoms diVer substantially. Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.molstruc. 2006.07.010.
125
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