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A novel reaction of selenobenzophenones with tetracyanoethylene. Formation of a 2,3-dihydroselenophene
e
Tetrahedron Leller•• Vol. 36. No. 48. pp. 8813-8816.
Pergamon
199~
ElsevIer Science Ltd Prinled ,n Great Brilain
0040-403919'
S9.~~.OO
0040-4039(95)01881-6
A Novel Reaction of Selenobenzophenones with Tetracyanoethylene. Formation of a 2,3.Dihydroselenophene. Kentaro Okuma,* Kei-ichiro Miyazaki, Seiji Okumura, Yoshikazu Tsujimoto, Kazuki Kojima, Hiroshi Ohla, and Yoshinobu Yolmmori t Departmenl of Chemistry, Faculty of Science. Fukuoka Uoivenity. Jonan-ku. Fukuoka 814-80. Japan
t Department of Chemistry. National Defense Academy. lIashirimizu. Yokosuka 239. Japan
Abstract: The reaction of selenobcnzophenones with tctracyanoethylene (TCNE) exclusively affords an unusual type of adduct with the structure of 2.3-dihydroselenophcne. sharply different from the reacI10n between thiobenzophenone and TCNE
Tetracyanoethylene (TCNE) has played an important role in extensive applications
In
organic
synthesis owing to its anomalous reactivity, I PrevIously, we reported the reactIon of tropothione With TCNE to afford 8.8-dicyanoheplafulvene via a (2 + 2)-type cycloaddition. 2 HUtsgen el 01. reported that thiobenzophenones (1) reacted with TCNE to give 2: 1 adducts of thiophene denvatlvcs (2) and six· membered cyclic disulfides (3) In moderate yields. 3 However, there is no report on the reaction of
NC Ar
""r-{
>=N)(S~N==<
Ar
NC
CN Ar Ar
CN
N-O-N Ar-<{ S -S }-Ar Ar Ar 3
selenoketones with TCNE. Recently, we have isolated selenobenzophenones (4), which reacted with olefins to afford several types of the corresponding cycloadducts. 4 We report herein an unusual reaction of selenobenzophenones with TCNE to give a novel type of cycloadducts (5), sharply different from the above result WIth thiobenzophenone. 4,4'_Dimethoxyselenobenzophenone (4a) reacted with a half mole equivalent of TCNE at room temperature to afford a novel type of cycloadduct (dihydroselenophene, Sa) as the sole product in 30% isolated yield (Scheme I). The product was identified as Sa on the basis of the spectroscopies. 5.6 8813
8814
MeO CN \ TCNE
toluene
CN~r OMe ~
,.
Sa
I~ DOM e
MeO
sa
4a
Scheme 1. Similarly. we have obtained dihydroselenophenes (Sa-c) in 21-71 % yields from the reactions of selenobenzophenones (generated in situ starting from diarylmethylenet riphenylphosphoranes in the presence of elemental selenium) with rCNE.7 When the reaction was carried out at 4O"C, the yields of
Ar\ 9=PPh 3
Ar
+ (Se)"
}
Benzene or
Xylene
..
NC
Ar,
TCNE
C=5e
Ar"
~
eN eN
Ar ~ Ar Ar sa N=( 'Ar
... Ar=p-MeOCeH4 4b Ar=p.MeCeH4 4c Ar=CeHs
51 Ar=p-MeOCeH4 5b Ar= p-MeCs ~ 5c Ar=CsHs
Scheme 2. 5 were reduced. However. we have found that the yields were improve d up to 48-11% , when the reaction was performed in renuxin g toluene (Table 1).8 Table 1. The Reaction of Selenobenzophenones with TCNE Sclenobcnzophenone
Ar
Conditions Solvent TemptC toluene benzene
renux reflux
toluene
40
Timelhr
toluene
renux
toluene
reflux
2 2 3 2 2
toluene
.40
3
Products (Yield/%)
Sa
71 50
Sb
42 70
5c
48
21
HUisgen et al. suggested that the reaction between thiobenzophenon e and TCNE proceeded through the initial attack of thiocarbonyl sulfur on nitrile via a [2 + 2] manner, followed by the attack of another thiobenzophenone on the same side of the nitrile to yield thioamid e derivatives. and the final sulfur extrusion formed five-membered cyclic thiophene derivatives, 2. 3
8815
A similar initial attack would occur in the reaction of selenobenzophenones with TCNE. However, a four-membered intermediate is more hindered than that from thiobcnzophenone, and is easily converted into ring-opened selenoamide (6). Another selenobenzophenone reacted With 6 via a [4 + 2] manner to afford the six-membered cyclic diselenide,9 which finally extruded selenium to give the 2,3• dihydroselenophene,5.
NC
NC eN '\.--
[2+2~
I:,;. At
Sa~
NC
~ -.. [" ~ NC _~N Ar~ C. Ar
Ar
SeAr
-
N...,
Sa Sa
l:i
NC
NC~N At -
CN
[4+2)
-sa
At
At
CN CN "
\ Se N
C(Ar)2
6
=<
At
'Ar
5
Scheme 3. We then tried the reaction of 4.4'-diOuoroselenobenzophenone with rCNE. In this case, the product was not a dihydroselenophene but a selenophene derivative (7) in 35% yield. lO While the mechanism of the formation of 7 is unclear at present, it is postulated that an electron-withdrawing group has some important role in this reaction.
F
~
o
C=PPh3
F
Scheme 4.
The first true synthesis of selenophene was realized about 70 years ago from acetylene and selenium. 11 Tetrahydroselenophene (selenolane) can be also prepared in several different ways.12 Nevertheless, there is no report on the synthesis of monocyclic dihydroselenophenes. S. The present result is the first formation of a dihydroselenophene. which may be proved to be an important intermediate for synthetic application from analogy with dihydrothiophenes. since dihydrothiophenes are widely applied to conversion into thiopyrylium salts by ring expansion. 13 This work was supported by a Grant-in-Aid for Scientific Research from the Ministry of Education, Science and Culture, Japan. References 1) Y. Masaki. r. Miura. and M. Ochiai. Chern. Lell., 1993. 17; A. C. Benniston, A. Harriman, D. Philp, and J. F. Stoddart. J. Am. Chern. Soc., liS, 5298 (1993); S. Dibella. I. L Fragala. M. A. Ratner, and T. J. Marks. J. Am. Chern. Soc., liS. 682 (1993); T. Kim. G. A. Mirafzal. and N. L. Bauld,
Tetrahedron Lell., 34,7201 (1993); V. Figala. T. Gessner. R. Gompper. E. Hadicke, and S. Lensky,
8816
Tetrahedron Lett.• 34,6375 (1993); For reviews, see: A. J. Fatiadi, Synthesis, 1986, 249; A. J. Fatiadi, Synthesis, 1987,749. 2)
T. Machiguchi, K. Okuma, M. Hoshino, and Y. Kitahara, Tetrahedron Lett., 1973,2011.
3)
1. R. Moran, R. Huisgen, and I. Kalwinsch, Tetrahedron Lett., 26, 1849 (1985).
4)
K. Okuma, K. Kojima, I. Kaneko, and H. Ohta, Chem. Lett., 1991, 1053; K. Okuma, K. Kojima, I. Kaneko, and H. Ohta, Tetrahedron Lett., 33, 1333 (1992); K. Okuma, K. Kojima, and H. Ohta,
Phosphorus, Sulfur, and Silicon, 80, 259 (1993); K. Okuma, K. Kojima, I. Kaneko, Y. Tujimoto, H. Ohta, and Y. Yokomori, J. Chem. Soc.• Perkin 1,1994,2151. 5)
Satisfactory elemental analyses w(;re obtained for all new compounds (5a-e and 7). Sa: Yellow needles; m. p. 225-226 ·C (methanol-ether). IR (KBr); 2100 cm- 1 (vCN). IH NMR (400 MHz, CDCIJ) 6=3.82 (s, 6 H, MeO), 3.89 (s, 6 H, MeO), 6.84 (d, 4 H, Ar), 6.93 (d, 4 H, Ar),
7.27 (d, 4 H, Ar), 7.50 (d, 4 H, Ar). Be NMR (100 MHz, CDC!) 6=54.9 (Ar2£,-Se), 55.2 (MeO), 55.3 (MeO), 55.5 (MeO), 55.6 (MeO), 70.6 [£(CN)2l, 89.4 (C=~-CN), 111.8 [C~Nhl, 113.9 (=C• ~N),
113.9, 114.1, 127.5, 129.6, 131.6, 132.5, 160.0, 163.1 (Ar), 163.4 (Se-C=), 173.3 (Ar2£,=N).
6)
The structure of Sa was also confirmed by X-ray analysis. Details of the X-ray result are to be
7)
published elsewhere. Selenobcnzophenones tend to be oxidized when exposed to air. 4 Sb: Yellow needles; m. p. 195-196 ·C. IH NMR (400 MHz, CDCI3) 6= 2.36 (s, 6H, Me), 2.44 (s,
8)
6H, Me), 7.12 (d, 4H, Ar), 7.21-7.25 (m, 8H, Ar), 7.42 (br d, 4H, Ar). BC NMR (100 MHz, CDCI3) 6=21.0 (Me), 21.7 (Me), 54.8 (Ar2-~-Se), 71.3 [£(CN)2l, 89.0 (C=~-CN), 111.6 [C(~Nhl, 113.3 (=C-~N), 128.2, 129,4, 129.4, 130.2, 132.5, 136.7, 139.4, 143.3 (Ar), 169.4 (C=~-Se), 174.1 (Ar2£,=N). Sc: Yellow needles, m. p. 218-219 ·C. IH NMR (400 MHz, CDCI3) 6=7.31-7.40 (Ar),
7.43-7.48 (Ar), 7.53-7.61 (Ar). BC NMR (100 MHz, CDCI3) 6=54.6 (Ar2-~-Se), 71.6 [QCN)2l, 89.2 (C=~-CN), 111.3 [C~N)2l, 113.0 (=C-~N), 128.3, 128.9, 129.4, 129.9, 132.5, 135.0, 139.4, 9)
168.9 (C=~-Se), 174.2 (Ar2£,=N). Another regioisomer (8) in the reaction of 6 with sclcnobcnzophenone might be a possible intermediate, which further extruded one mole of selenium to afford S.
CN
CN
NC'f--t..-
srf,
')-N
Ar)-se Ar
~Ar
8
Ar
10) 7: Orange needles; m. p. 306-308 ·C. IR (KBr); 2100 cm- 1 (vCN). IH NMR (400 MHz, CDC I3)
b=7.09 (broad d, 8H), 7.79 (broad d, 8H). BC NMR (100 MHz, CDC!J) b=96.1 (=~-CN), 110.1,
113.4 (~N), 116.3 (Ar), 132.0 (Ar), 133.7 (Ar), 160.7 (Ar2~=N), 166.0 (=~-Se).
II) F. Mazza and L. Solazzo, Rend. Acad. Sci. Napoli, 33,236 (1927). 12) 1. D. McCullough and A. Lefohn,1norg. Chem., 5, ISO (1966). G. T. Morgan and F. H. Burstall, J. Chem. Soc., 1929, 1096. Yu. K. Yue'ev, J. Gen. Chem. (USSR), 16,851 (1946). 13) R. Pettit, Tetrahedron Lett., 1960, II.
(Received in Japan 17 July 1995; revised 27 September 1995; accepted 6 October 1995)
Tetrahedron Leller•• Vol. 36. No. 48. pp. 8813-8816.
Pergamon
199~
ElsevIer Science Ltd Prinled ,n Great Brilain
0040-403919'
S9.~~.OO
0040-4039(95)01881-6
A Novel Reaction of Selenobenzophenones with Tetracyanoethylene. Formation of a 2,3.Dihydroselenophene. Kentaro Okuma,* Kei-ichiro Miyazaki, Seiji Okumura, Yoshikazu Tsujimoto, Kazuki Kojima, Hiroshi Ohla, and Yoshinobu Yolmmori t Departmenl of Chemistry, Faculty of Science. Fukuoka Uoivenity. Jonan-ku. Fukuoka 814-80. Japan
t Department of Chemistry. National Defense Academy. lIashirimizu. Yokosuka 239. Japan
Abstract: The reaction of selenobcnzophenones with tctracyanoethylene (TCNE) exclusively affords an unusual type of adduct with the structure of 2.3-dihydroselenophcne. sharply different from the reacI10n between thiobenzophenone and TCNE
Tetracyanoethylene (TCNE) has played an important role in extensive applications
In
organic
synthesis owing to its anomalous reactivity, I PrevIously, we reported the reactIon of tropothione With TCNE to afford 8.8-dicyanoheplafulvene via a (2 + 2)-type cycloaddition. 2 HUtsgen el 01. reported that thiobenzophenones (1) reacted with TCNE to give 2: 1 adducts of thiophene denvatlvcs (2) and six· membered cyclic disulfides (3) In moderate yields. 3 However, there is no report on the reaction of
NC Ar
""r-{
>=N)(S~N==<
Ar
NC
CN Ar Ar
CN
N-O-N Ar-<{ S -S }-Ar Ar Ar 3
selenoketones with TCNE. Recently, we have isolated selenobenzophenones (4), which reacted with olefins to afford several types of the corresponding cycloadducts. 4 We report herein an unusual reaction of selenobenzophenones with TCNE to give a novel type of cycloadducts (5), sharply different from the above result WIth thiobenzophenone. 4,4'_Dimethoxyselenobenzophenone (4a) reacted with a half mole equivalent of TCNE at room temperature to afford a novel type of cycloadduct (dihydroselenophene, Sa) as the sole product in 30% isolated yield (Scheme I). The product was identified as Sa on the basis of the spectroscopies. 5.6 8813
8814
MeO CN \ TCNE
toluene
CN~r OMe ~
,.
Sa
I~ DOM e
MeO
sa
4a
Scheme 1. Similarly. we have obtained dihydroselenophenes (Sa-c) in 21-71 % yields from the reactions of selenobenzophenones (generated in situ starting from diarylmethylenet riphenylphosphoranes in the presence of elemental selenium) with rCNE.7 When the reaction was carried out at 4O"C, the yields of
Ar\ 9=PPh 3
Ar
+ (Se)"
}
Benzene or
Xylene
..
NC
Ar,
TCNE
C=5e
Ar"
~
eN eN
Ar ~ Ar Ar sa N=( 'Ar
... Ar=p-MeOCeH4 4b Ar=p.MeCeH4 4c Ar=CeHs
51 Ar=p-MeOCeH4 5b Ar= p-MeCs ~ 5c Ar=CsHs
Scheme 2. 5 were reduced. However. we have found that the yields were improve d up to 48-11% , when the reaction was performed in renuxin g toluene (Table 1).8 Table 1. The Reaction of Selenobenzophenones with TCNE Sclenobcnzophenone
Ar
Conditions Solvent TemptC toluene benzene
renux reflux
toluene
40
Timelhr
toluene
renux
toluene
reflux
2 2 3 2 2
toluene
.40
3
Products (Yield/%)
Sa
71 50
Sb
42 70
5c
48
21
HUisgen et al. suggested that the reaction between thiobenzophenon e and TCNE proceeded through the initial attack of thiocarbonyl sulfur on nitrile via a [2 + 2] manner, followed by the attack of another thiobenzophenone on the same side of the nitrile to yield thioamid e derivatives. and the final sulfur extrusion formed five-membered cyclic thiophene derivatives, 2. 3
8815
A similar initial attack would occur in the reaction of selenobenzophenones with TCNE. However, a four-membered intermediate is more hindered than that from thiobcnzophenone, and is easily converted into ring-opened selenoamide (6). Another selenobenzophenone reacted With 6 via a [4 + 2] manner to afford the six-membered cyclic diselenide,9 which finally extruded selenium to give the 2,3• dihydroselenophene,5.
NC
NC eN '\.--
[2+2~
I:,;. At
Sa~
NC
~ -.. [" ~ NC _~N Ar~ C. Ar
Ar
SeAr
-
N...,
Sa Sa
l:i
NC
NC~N At -
CN
[4+2)
-sa
At
At
CN CN "
\ Se N
C(Ar)2
6
=<
At
'Ar
5
Scheme 3. We then tried the reaction of 4.4'-diOuoroselenobenzophenone with rCNE. In this case, the product was not a dihydroselenophene but a selenophene derivative (7) in 35% yield. lO While the mechanism of the formation of 7 is unclear at present, it is postulated that an electron-withdrawing group has some important role in this reaction.
F
~
o
C=PPh3
F
Scheme 4.
The first true synthesis of selenophene was realized about 70 years ago from acetylene and selenium. 11 Tetrahydroselenophene (selenolane) can be also prepared in several different ways.12 Nevertheless, there is no report on the synthesis of monocyclic dihydroselenophenes. S. The present result is the first formation of a dihydroselenophene. which may be proved to be an important intermediate for synthetic application from analogy with dihydrothiophenes. since dihydrothiophenes are widely applied to conversion into thiopyrylium salts by ring expansion. 13 This work was supported by a Grant-in-Aid for Scientific Research from the Ministry of Education, Science and Culture, Japan. References 1) Y. Masaki. r. Miura. and M. Ochiai. Chern. Lell., 1993. 17; A. C. Benniston, A. Harriman, D. Philp, and J. F. Stoddart. J. Am. Chern. Soc., liS, 5298 (1993); S. Dibella. I. L Fragala. M. A. Ratner, and T. J. Marks. J. Am. Chern. Soc., liS. 682 (1993); T. Kim. G. A. Mirafzal. and N. L. Bauld,
Tetrahedron Lell., 34,7201 (1993); V. Figala. T. Gessner. R. Gompper. E. Hadicke, and S. Lensky,
8816
Tetrahedron Lett.• 34,6375 (1993); For reviews, see: A. J. Fatiadi, Synthesis, 1986, 249; A. J. Fatiadi, Synthesis, 1987,749. 2)
T. Machiguchi, K. Okuma, M. Hoshino, and Y. Kitahara, Tetrahedron Lett., 1973,2011.
3)
1. R. Moran, R. Huisgen, and I. Kalwinsch, Tetrahedron Lett., 26, 1849 (1985).
4)
K. Okuma, K. Kojima, I. Kaneko, and H. Ohta, Chem. Lett., 1991, 1053; K. Okuma, K. Kojima, I. Kaneko, and H. Ohta, Tetrahedron Lett., 33, 1333 (1992); K. Okuma, K. Kojima, and H. Ohta,
Phosphorus, Sulfur, and Silicon, 80, 259 (1993); K. Okuma, K. Kojima, I. Kaneko, Y. Tujimoto, H. Ohta, and Y. Yokomori, J. Chem. Soc.• Perkin 1,1994,2151. 5)
Satisfactory elemental analyses w(;re obtained for all new compounds (5a-e and 7). Sa: Yellow needles; m. p. 225-226 ·C (methanol-ether). IR (KBr); 2100 cm- 1 (vCN). IH NMR (400 MHz, CDCIJ) 6=3.82 (s, 6 H, MeO), 3.89 (s, 6 H, MeO), 6.84 (d, 4 H, Ar), 6.93 (d, 4 H, Ar),
7.27 (d, 4 H, Ar), 7.50 (d, 4 H, Ar). Be NMR (100 MHz, CDC!) 6=54.9 (Ar2£,-Se), 55.2 (MeO), 55.3 (MeO), 55.5 (MeO), 55.6 (MeO), 70.6 [£(CN)2l, 89.4 (C=~-CN), 111.8 [C~Nhl, 113.9 (=C• ~N),
113.9, 114.1, 127.5, 129.6, 131.6, 132.5, 160.0, 163.1 (Ar), 163.4 (Se-C=), 173.3 (Ar2£,=N).
6)
The structure of Sa was also confirmed by X-ray analysis. Details of the X-ray result are to be
7)
published elsewhere. Selenobcnzophenones tend to be oxidized when exposed to air. 4 Sb: Yellow needles; m. p. 195-196 ·C. IH NMR (400 MHz, CDCI3) 6= 2.36 (s, 6H, Me), 2.44 (s,
8)
6H, Me), 7.12 (d, 4H, Ar), 7.21-7.25 (m, 8H, Ar), 7.42 (br d, 4H, Ar). BC NMR (100 MHz, CDCI3) 6=21.0 (Me), 21.7 (Me), 54.8 (Ar2-~-Se), 71.3 [£(CN)2l, 89.0 (C=~-CN), 111.6 [C(~Nhl, 113.3 (=C-~N), 128.2, 129,4, 129.4, 130.2, 132.5, 136.7, 139.4, 143.3 (Ar), 169.4 (C=~-Se), 174.1 (Ar2£,=N). Sc: Yellow needles, m. p. 218-219 ·C. IH NMR (400 MHz, CDCI3) 6=7.31-7.40 (Ar),
7.43-7.48 (Ar), 7.53-7.61 (Ar). BC NMR (100 MHz, CDCI3) 6=54.6 (Ar2-~-Se), 71.6 [QCN)2l, 89.2 (C=~-CN), 111.3 [C~N)2l, 113.0 (=C-~N), 128.3, 128.9, 129.4, 129.9, 132.5, 135.0, 139.4, 9)
168.9 (C=~-Se), 174.2 (Ar2£,=N). Another regioisomer (8) in the reaction of 6 with sclcnobcnzophenone might be a possible intermediate, which further extruded one mole of selenium to afford S.
CN
CN
NC'f--t..-
srf,
')-N
Ar)-se Ar
~Ar
8
Ar
10) 7: Orange needles; m. p. 306-308 ·C. IR (KBr); 2100 cm- 1 (vCN). IH NMR (400 MHz, CDC I3)
b=7.09 (broad d, 8H), 7.79 (broad d, 8H). BC NMR (100 MHz, CDC!J) b=96.1 (=~-CN), 110.1,
113.4 (~N), 116.3 (Ar), 132.0 (Ar), 133.7 (Ar), 160.7 (Ar2~=N), 166.0 (=~-Se).
II) F. Mazza and L. Solazzo, Rend. Acad. Sci. Napoli, 33,236 (1927). 12) 1. D. McCullough and A. Lefohn,1norg. Chem., 5, ISO (1966). G. T. Morgan and F. H. Burstall, J. Chem. Soc., 1929, 1096. Yu. K. Yue'ev, J. Gen. Chem. (USSR), 16,851 (1946). 13) R. Pettit, Tetrahedron Lett., 1960, II.
(Received in Japan 17 July 1995; revised 27 September 1995; accepted 6 October 1995)