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Unusual rearrangement of triangulane gem-dibromides in the presence of methyllithium.
Vol.48.No.45.pp.9977-9984.1992 Rited in Great Britain
oo4uo2ot92 s5.00+.00 Pergsmon Ress Lid
Tetrahedron
Unusual Rearrangement of Triangulane gem-Dibromides in the Presence of Methyllithium. Kit-ill A. Lukin. Nikolai S. Zef&ov* DepartmentOfchemistry,MOSCOW SlateUnivusity, Moseow.119899, Russia, Dmitri S. Yufit, Ywi
T. Struchkov
AN. NesmeyanovInstituteof OrganoelementCompounds,Vavilov St. 28.117813, hWcow, Russia.
(Received in UK 8 July 1992)
Abstract: Triangulanegemdibromides in the presence of methyllithiumundergorearrangementof di&mmospimpentyl One.
fragment into l-~methyl-Z-~~yclobutenyt
Ring opening of cyclopropane
gm-dibmmides
with methyllithium
is one of the widely wed pmparative
routes to allene~.~ The accepted mechanism of this reaction includes lithium - bromine exchange to yield bm~~~i~~id,
which is not stable at temperatures higher then -90 OC! and undergoes a loss of lithium
bromide. Resulting cyclopropylidene rearranges to allene simultaneously (eq 1).2 Known side reactions in&de: a) electrophiiic substitution of lithium in bromolithiocarbenoid3 and b) inter or intramokzcular insertions4 or cycloaddition~~ associated with the intermediacy of cyclopropylidene.
Li
A =
[D:]
-
cc=
(1)
Br
Br Mel.1
cc-
(2)
-D 1
In the
course of our studies of
ne~,~ known transformation
1
triangulanes,
hydrocarbons
of dibromospiropentane
constructed from spimannulated cyclopropa-
1 into vinylidenccyclopropanne 2 (eq 2) was successfully
applied in the synthesis of branched triangt~lanes.~
9977
9978
K. A. LUKINer al.
However, mom detailed examination of this reaction and attempted preparation of other allenes from different triangulane gem-dibromldes allowed us to find a new unusual rearmnge~nt of the letter compounds in the presence of methyllithium. The results are summarized in this paper.
Results and discussion. Reaction of 7,7-dibromodispirol2.2.llheptane
3 with methyllithium. This reaction was reported
to give expected bis(cyclopmpylidene)methane 4 in 85% yield8 However no experimental detailes or properties of allene 4 were reported8 To our surprixe, treatment of dllxomide 3 with methyllithium at -55 OC resulted in formation of two products in 1: 2 ratio aumrding to GC analysis. lH and 13C NMR study allowed to assign structure of allene 4 to the lirst , minor component of reaction mixture. The major component was shown to be 2-bromo-1-(1-bmmocyclopmpyl)cyclobutene (5) - isomer of starting dibromide 3 (Scheme I). Scheme
3
1
4
Whenthesamereacdonwascarriedoutat-5OCt~w:pfoductsin8:l:lmdoweredetectedbyGC.Inthis case allene 4 was the main product and it was isolated in 60% yield. ‘Ihe second component was dibromide 5 and the third component was shown to be 1-(1-bromocyclopropyl)-2-iodocyclobutene (6). Finally, when the reaction of dlbromide 3 and methyllithium was carried at +5 - +8 OC only allene 4 and mixed halide 6 were detected in the reaction mixture, accompanied witb large amount of polymeric material. This type of halogen exchange was reported in literature and was associated with the presence of LiI, if ~~y~~~ was prepared from iodomethane.g It was demonstrated that the rate of halogen exchange was negligible at -40 oC, but became important at higher temperauues.g Thus we have found, that treatment of dibromide 3 with methyl lithium resuhs in formation of both allene 4 and rearrauged dihalides S,6, with lower t~~mt~ favoured pageant. These results prompted us to investigate reactions of other triangulane gem-dilxomides with methyllithium. Reactions of dibromospiropentane (1) and dibromodispiro[2.2.1]heptane (7) with MeLi. We have found earlier that the yield of allene 2 was increased with the increase of temperature of the reaction of dibromospiropentane 1 with methyllithium. However, the nature of byproducts in this reaction was never studied. When the reaction was carried out at -50 OC. distillation of the residue, obtained after evaporation of allene 2 and other volatiles, gave only one product, which was assigned structure 8 based on 1H and 13C spectra (Scheme II).ll
Unusual rearrangement of triangulane gem-dibromides
9979
CHzBr I
Direct reduction of this residue with lithium in rer&butanol gave, according to GC, only one product,which was isolated by distillation and shown to be known l.l’-(1,2-ethanediyl)biscyclobutene (9).12 Formation of compound 8 could be accounted for by rearrangement of dibromide 1 to 1-bromo-1-(bromomethyl)cyclobutene @a). which undergoes immediate coupling in the presence of MeLi. scllemrIn
l
-
.._
llb
“C
Compound 7 was the third uiangulane dibromide studied in reaction with MeLi. In this case, formation of vinylidenespiropentane 10 could be expected to accompany with three isomeric rearranged bromides Ha-c. However, when this reaction was carried out at -50 OC only traces of allene 10 were detected by GC. Column chromatography of a residue, obtained after evaporation of volatiles. gave two fractions. lH and 13C NMR spectra of the fraction 1 indicated, that it contained one of the two possible symmetric isomers of compound 11, however it was not possible to choose between structures 11s and llb. Reduction of this dibromide with lithium in tert-butanol gave hydrocarbon which was tentatively assigned structure 12 based on lH NMR spectrum. This structural assignment was unambigeously supported by X-ray structural analysis. The first (to our knowledge) sttucture of spirohexene compound is outlined in figure 1.
K.A. Ltnm et al.
lH and 13C NMR study of the second fraction indicated that it was 1:l mixtme of compound llaand dibromide 13. Formation ofcompound13 could be accounted for by allylic mode of coupling of intermediate bromide 14inpresense of MeLi. Such mcde of coupting was found in the case of l-~m~me~y~~yci~ bt~te.ne.~~Thus it was found that narmngement of dibmmide 7 proceeded in a selective manner to yield prrt ducts, that could be associated only with formation of intermediate 14.
In conclusion, we have found a new type of reaction of cyclopmpane gem-dibnxnides in the presence of methyllithium. This reaction is characteristic for aiaqu.lanes gernditromides and includes rearrangement of dibmmoqimpentane fiagment into 2-bromt+ l-(IxxxnomethyQcyclobutene one as a key step. Such rearrangement could be hardly associated with ~~~~~n~d or cyclic interme&q. While mechanistic aspects of thii xeaction remain to be clarified,~3 it opens a new useful synthetic approach to compounds with bromocyclobutenyl and cyclobutenyl moieties.
Unusual rearrangement of triangulane gem-dibromides
9981
Experimental Section. General. ‘H and 13C NMR spectra were recorded in CDCl3 GC analysis was carried out with a 3000 x 3 mm column packed with SE-30 on Jnerton NAW phase. Mass spectra were obtained at 12 eV. l,l-Dibromospiropentane (l), 7,7-dibromodispiro[2.2.l]heptane (3). and l,l-dibromodispiro[2.2.1]heptane (7) were prepared by cycloaddition of dibromocarbene to cortesponding olefiis according to a literature procedure.1o Reaction of Dibromide 3 with Metbylithium. To a magnetically sthred solution of dibromide 3 (14 mmol. 3.53 g) in dry ether (10 mL), methyllithium (19 mmol, 16 nL of 1.2 N solution in ether) was added dropwise over 0.5 h at -50 - -55 OC under argon. The reaction mixture was then allowed to warm to 0 OC and quenched with water. The organic layer was separated, washed with water and dried with MgSO4 The solvent was evaporated and fractional distillation of the residue gave allene 4 and dibromide 5. Bis(cyclopropylidene)methane (4)14 was obtained in 21% yield: *H NMR 6 1.48 (s); 13C NMR 6 7.38 (4 C). 80.98 (2 C), 176.57 (1 C). 2-Bromo-1-(l-bromocyclopropyl)cyclobutene
(5): 1.7 g. 48%; bp 54-56 OC (3 mm); lH NMR (250
MHz) 6 1.29 (m, 2 H), 1.38 (m, 2 H). 2.60 (m, 2 H), 2.64 (m, 2 H); 13C NMR 6 16.39 (t. J = 166 Hx. 2 C), 25.67 (s. 1 C), 30.80 (t, J = 143 Hz, 1 C), 33.67 (t, J = 143 Hz, 1 C), 108.47(s, 1 C), 146.43 (s, 1 C); Anal. Calcd for C7H8Br2: C, 33.36; H, 3.20. Found: C, 33.22; H. 3.23. When this reaction was carried out at -5 - -7 OC allene 4 was isolated in 60 46 yield; dibromide 5 was obtained in 10% yield and new product - bromoiodide 6 was isolated in 11% yield 1-(1-Bromocyclopropyl)-2-iodocyclobutene
(6): bp 62 - 63 OC (3 mm); nD20 1.6053; *H NMR
(250 MHz) 6 1.28 (m, 2 H), 1.36 (m, 2 H), 2.65 (m, 2 H); 2.80 (m, 2 H); 13C NMR 6 15.92 (2 C). 26.66, 34.43, 35.01, 82.08, 153.94. MS (m/e): 300,298 (M+), 220, 173. 171.92 (base), 91. When the same reaction was carried out at +5 - +8.OC only allene 4 and iodide 6 were obtained in 19% and 33% yield, respectively. 1,2-Bis(2-bromo-1-cyclobutenyl)ethane (8). Reaction of dibromospiropentane 1 with methyllithium was carried out in accord with the procedure given above. Allene 2. which was produced in 25% yield, and the solvent were distilled into a cold to -78 OC trap. Distillation of the residue gave dibromide (8) in 1.16 g, 27% yield; bp 91-94 OC (2 mm); lH NMR (250 MHz) 6 2.21 (br s, 4 H), 2.51 (m, 4 H), 2.71 (m. 4 H); 13C NMR 8 25.47 (t, J = 129 Hz), 30.49 (t, J = 142 Hz), 35.08 (t. J = 142 Hz), 108.52 (s), 147.40 (s). Anal. Calcd for ClOHl2Br2: C, 41.13; H, 4.14. Found: C, 41.38; H. 4.02. Reaction of l,l-Dibromodispiro[2.2.l]heptane (7) with methyllithium was carried out in accord with the procedure given above. The solvent was evaporated and column chromatography of the residue gave: fraction 1 - dibromide lla, and fraction 2 - 1:l mixture of dibromides lla and 13. 1,2-Bis(2-bromospirohex-4-ene-4-yl)ethane
(lla):
1.03 g, 43%; mp 37 OC; lH NMR (250 MHz) 6
9982
K. A. LUKINet al.
0.77 (s, 8 H), 2.0 (s, 4 I-l), 2.80 (s, 4 I-I); 13C NMR 6 6.63 (t, J = 162 Hz). 22.64 (t, J = 130 Hz), 30.94 (s). 45.11 (t, J = 142 Hz), 104.34 (s), 149.48 (s). Anal. Calcd for Cl4Hl6Br2: C, 48.86; H, 4.69. Found: C, 49.03; H, 4.42. 5-Bromo-4-[(5-bromo-4-methylenespirobex-S-yl)methyl]spirohex-4-ene
(13): lH NMR (250
MHz) 6 0.79 (s, 4 H), 0.8 - 1.0 (m, 4 I-I), 2.7 - 2.9 (m, 6 I-l), 4.58 (d, J = 1.75 Hz, 1 I-I), 4.97 (d, J = 175 Hz, 1 II); 13C NMR 6 7.02, 7.36, 14.86 (2 C), 31.48, 31.91, 40.48, 45.46, 46.46, 58.95, 101.49, 111.00, 147.51, 162.28. For a mixture of bromides lla and 13 anal. calcd for Cl4Hl6Br2: C. 48.86, II, 4.69. Found: C. 48.49; H, 4.68. Reduction of Dibromides 8 and lla with Lithium in tert-Butanol. Preparation of Hydra. carbons 9 and 12. To a stirred solution of dibromide (8 mmol) and tert-butanol(3.8 mL. 40 mmol) in dry TI-IF (25 mL), lithium tunings (0.35 g, 50 mmol) were added portionwise, allowing gentle boiling of reaction mixture. After 3 h pentane (25 mL) and water (50 rnL) were added. Permute layer was washed with water (3 x 50 m.L), dried with MgS04 and the solvent was evaporated. Olefins 9 and I2 were isolated by distillation. l&Bis(l-cyclobutenyI)ethane
(9) was isolated in 0.74 g, 69% yield: bp 75-76 OC (20 mm). lH NMR
was in accord with literature data12 If-Bis(spirohex-4.ene-4.yl)ethane
(12) was isolated in 78% yield: mp 43 OC; lH NMR (250 MHz)
6 0.7 (s, 8 I-I), 1.93 (s, 4 I-I), 2.49 (s, 4 I-Q, 5.78 (s. 2 H); 13C NMR 6 6.62, 23.33, 30.39, 37.25, 123.80, 152.48.
X-ray Structural Analysis of l&Bis(spirohex-4-ene-4.yl)ethane
(12).
Data collection was performed from the transparent prism-shape crystal with Siemens P3/PC four circle diffractometer using graphite monochromatized MO K, radiation. Hydrocarbon 12. Monoclinic crystalls. Cell parameters at -90 OC: a = 9X5(6) A; b = 5.373(3) & c = 11.981(6) A; a = 900; p = 112.09(4)O; y= 900. Vol = 553.8 (1.1) A3. Unit contents: Cl4Hl8, Z = 2. Density: 1.117 g/cm3 . Space group: P2( 1)/C. Intensity data were collected on 1364 reflections (871 with I > 4s). Final R = 0.050; Rw = 0.049.The structure has been solved by direct method and refmed by full-matriz least squares anisotropically. All H-atoms were obtained from the difference Fourier map andrefined isotropically. Programm SI-IRLX PLUS (PC) version was used in all calculations. Structural data am collected in Tables 1 - 5. Table 1. Atomic coordinates (~1~) and temperature factors (k103). Atom C(1) C(3) C(5) C(7) ______
x
Y
Z
9469(2) 3982(4) 10068(2) 8649(3) 2559(5) 7817(2) 7218(2) 943(4) 8579(2) 5775(3) 1152(5) 8868(2)
U*
Atom
25(l) 31(l) 27(l) 33(l)
C(2) C(4) C(6)
x
Y
8565(2) 2705(4) 7317(3) 701(5) 6874(3) -1007(5)
z 8912(2) 7319(2) 9338(2)
*Equivalent isotropic U defined as one thii of the trace of the orthogonal&d U(ij) tensor.
U* 24(l) 33(l) 32(l)
Unusual rearrangement of triangulane gem-dibromides
9983
Table 2. Bond L.enths (A). C(l)-C(2) C(l)-C(la) C(2)-C(3)
1.490(3) 1.522(S) 1.344(3)
C(2)-C(5) C(3)-C(4) C(4)-C(5)
1.498(3) 1.52X3) 1.552(3)
C(5)-C(6) C(S)-C(7) C(6)-C(7)
1.499(4) 1.509(4) 1.507(4)
Table 3. Bond Angles (deg). C(2)-C(l)-C(la) C(4)-C(5)-C(6) C(3)-C(2)-C(5) C(6)-C(S)-C(7) C(2)-C(5)-C(4)
113.1(2) 129.5(2) 93.0(2) 60.1(2) 87.9(2)
C(2)-C(5)-C(6) C(l)-C(2)-C(5) C(4)-C(5)-C(7) C(3)-C(4)-C(5) C(5)-C(7)-C(6)
128.9(2) 131.3(2) 127.7(2) 84.3(2) 59.6(2)
C(l)-C(2)-C(3) C(2)-C(5)-C(7) C(2)-C(3)-C(4) C(5)-C(6)-C(7)
135.6(2) 128.1(2) 94.8(2) 60.3(2)
Table 4. Anisotropic Temperature Factors (A2 x 105. Atom
Ull
U22
u33
C(1) C(3) C(5) C(7)
28(l) 33(l) 25(l) 26(l)
27(l) 38(l) 33(l) 42(l)
21(l) 28(l) 23(l) 34(l)
U23 l(1) -5(l) -2(l) 4(l)
U13
U16
Atom Ull
U22
U33
U23
U13
U16
11(l) 16(l) 11(l) 14(l)
l(1) -6(l) O(1) O(1)
C(2) 25(l) C(4) 33(l) C(6) 32(l)
26(l) 42(l) 30(l)
22(l) 25(l) 34(l)
-l(l) -6(l) 5(l)
11(l) l(1) 13(l) -4(l) 12(l) -2(l)
Table 5. Hydrogen Coordinates (~10~) and Temperature Factors (A2 x 102).
Atom H(11) H(3) ~(42) H(62) H(72)
X
1005 934 638 752 577
Y 279 350 134 -101 253
z 1062 746 662 1019 944
U
Atom
X
Y
3 4 3 4 4
H(12) H(41) H(61) H(71)
874 764 657 480
474 -98 -267 84
Z
1042 716 900 826
U 3 2 3 4
K. A. LUKINet al.
References and Notes 1. Hopf, H. In Patai, S. Ed.; The Chemistry of Kerenes, AlIenes and Related Compounds, Part 2; Wiley: New York, 1980; Chapter 2. 2. Kirmse., W. Carbene Chemistry; Academic: New York, 1971,302 p. 3. For examples, see: a) Nilsen, N.O.; Skattebol, L.; Baird, MS.; Buxton, S.R.; Slowey, P.D. Tetrahedron L.ett. 1984,25, 2887-2890, b) Semmler, K.; Szeimies, G.; Belzner, J. J. Am. Chem. Sot. 1985,107, 6410-6411. 4. For examples, see: a) Moor, W.R.; Ward, H.R.; Menit, R.F. J. Am. Chem. Sot. 1961,83, 2019-2020; b) Brown, D.W.; Hengrick, ME.; Jones, M. Tetrahedron Lett. 19’73,3951-3954; c) Scattebol, L.; Stenstrom, Y.; Stjema. M.-B. Acra Chem. Stand. 1988,B42.475-483. 5. Scattebol, L. Chem. and Industry 1962,2146. 6. Zefirov, N.S.; Kozhushkov. S.I.; Kuznetzova, T.S.; Kokoreva, O.V.; Lukin. K.A.; Ugrak. B.I.; Tratch, S.S. J. Am. Chem. Sot. 1990.112. 7702-7707. 7. Lukin, K.A.; Kozhushkov. S.I.; Andrievski. A.A.; Ugrak, B.I.; Zefuov. N.S. J. Org. Chem. 1991,56. 6176-6179. 8. Fitjer, L.; Conia, J.M. Angew. Chem. 1973,85, 832-833. 9. Barlet. R.; Vincens, M. Tetrahedron 1977.33, 1291-1302. 10. Lukin. K.A.; Zefirov. N.S. Zh. Org. Khim. 1987,23, 2548-2552. 11. lH NMR of a crude product indicated - 10% of admixture that was tentatively assigned structure of 2brome l-[( 1-bmmo-2-methylenecyclobutyl)methyl]cyclobutene. However, this compound decomposed during attempted isolation by distillation or column chromatography. 12. Shea, K.J.; Wise, S. J. Org. C&m. 1978,43, 2710-2711. 13. No changes in lH NMR of dibromospiropentane were observed after 12 h stirring with a solution of dry lithium bromide in ether, Compound 8 was the main product of the reaction when butyllithium was used instead of methyllithium at -50 PC. However. I-bromo-1-lithiospiropentane was obtained and characterized by nucleophilic additions to aldehydes when this reaction was carried out at -110 PC (unpublished results), 14. a) Kopp, R.; Hanack, M. Angew. Chem. Internat. Edit. 1975,X4.821-822.b) Eckert-Maksic. M.; Zollner, S.; Gothling, W.; Boese. R.; Macsimovic, L.; Machinek, R.; De Meijere, A. Chem. Ber. 1991. 124, 1591.
oo4uo2ot92 s5.00+.00 Pergsmon Ress Lid
Tetrahedron
Unusual Rearrangement of Triangulane gem-Dibromides in the Presence of Methyllithium. Kit-ill A. Lukin. Nikolai S. Zef&ov* DepartmentOfchemistry,MOSCOW SlateUnivusity, Moseow.119899, Russia, Dmitri S. Yufit, Ywi
T. Struchkov
AN. NesmeyanovInstituteof OrganoelementCompounds,Vavilov St. 28.117813, hWcow, Russia.
(Received in UK 8 July 1992)
Abstract: Triangulanegemdibromides in the presence of methyllithiumundergorearrangementof di&mmospimpentyl One.
fragment into l-~methyl-Z-~~yclobutenyt
Ring opening of cyclopropane
gm-dibmmides
with methyllithium
is one of the widely wed pmparative
routes to allene~.~ The accepted mechanism of this reaction includes lithium - bromine exchange to yield bm~~~i~~id,
which is not stable at temperatures higher then -90 OC! and undergoes a loss of lithium
bromide. Resulting cyclopropylidene rearranges to allene simultaneously (eq 1).2 Known side reactions in&de: a) electrophiiic substitution of lithium in bromolithiocarbenoid3 and b) inter or intramokzcular insertions4 or cycloaddition~~ associated with the intermediacy of cyclopropylidene.
Li
A =
[D:]
-
cc=
(1)
Br
Br Mel.1
cc-
(2)
-D 1
In the
course of our studies of
ne~,~ known transformation
1
triangulanes,
hydrocarbons
of dibromospiropentane
constructed from spimannulated cyclopropa-
1 into vinylidenccyclopropanne 2 (eq 2) was successfully
applied in the synthesis of branched triangt~lanes.~
9977
9978
K. A. LUKINer al.
However, mom detailed examination of this reaction and attempted preparation of other allenes from different triangulane gem-dibromldes allowed us to find a new unusual rearmnge~nt of the letter compounds in the presence of methyllithium. The results are summarized in this paper.
Results and discussion. Reaction of 7,7-dibromodispirol2.2.llheptane
3 with methyllithium. This reaction was reported
to give expected bis(cyclopmpylidene)methane 4 in 85% yield8 However no experimental detailes or properties of allene 4 were reported8 To our surprixe, treatment of dllxomide 3 with methyllithium at -55 OC resulted in formation of two products in 1: 2 ratio aumrding to GC analysis. lH and 13C NMR study allowed to assign structure of allene 4 to the lirst , minor component of reaction mixture. The major component was shown to be 2-bromo-1-(1-bmmocyclopmpyl)cyclobutene (5) - isomer of starting dibromide 3 (Scheme I). Scheme
3
1
4
Whenthesamereacdonwascarriedoutat-5OCt~w:pfoductsin8:l:lmdoweredetectedbyGC.Inthis case allene 4 was the main product and it was isolated in 60% yield. ‘Ihe second component was dibromide 5 and the third component was shown to be 1-(1-bromocyclopropyl)-2-iodocyclobutene (6). Finally, when the reaction of dlbromide 3 and methyllithium was carried at +5 - +8 OC only allene 4 and mixed halide 6 were detected in the reaction mixture, accompanied witb large amount of polymeric material. This type of halogen exchange was reported in literature and was associated with the presence of LiI, if ~~y~~~ was prepared from iodomethane.g It was demonstrated that the rate of halogen exchange was negligible at -40 oC, but became important at higher temperauues.g Thus we have found, that treatment of dibromide 3 with methyl lithium resuhs in formation of both allene 4 and rearrauged dihalides S,6, with lower t~~mt~ favoured pageant. These results prompted us to investigate reactions of other triangulane gem-dilxomides with methyllithium. Reactions of dibromospiropentane (1) and dibromodispiro[2.2.1]heptane (7) with MeLi. We have found earlier that the yield of allene 2 was increased with the increase of temperature of the reaction of dibromospiropentane 1 with methyllithium. However, the nature of byproducts in this reaction was never studied. When the reaction was carried out at -50 OC. distillation of the residue, obtained after evaporation of allene 2 and other volatiles, gave only one product, which was assigned structure 8 based on 1H and 13C spectra (Scheme II).ll
Unusual rearrangement of triangulane gem-dibromides
9979
CHzBr I
Direct reduction of this residue with lithium in rer&butanol gave, according to GC, only one product,which was isolated by distillation and shown to be known l.l’-(1,2-ethanediyl)biscyclobutene (9).12 Formation of compound 8 could be accounted for by rearrangement of dibromide 1 to 1-bromo-1-(bromomethyl)cyclobutene @a). which undergoes immediate coupling in the presence of MeLi. scllemrIn
l
-
.._
llb
“C
Compound 7 was the third uiangulane dibromide studied in reaction with MeLi. In this case, formation of vinylidenespiropentane 10 could be expected to accompany with three isomeric rearranged bromides Ha-c. However, when this reaction was carried out at -50 OC only traces of allene 10 were detected by GC. Column chromatography of a residue, obtained after evaporation of volatiles. gave two fractions. lH and 13C NMR spectra of the fraction 1 indicated, that it contained one of the two possible symmetric isomers of compound 11, however it was not possible to choose between structures 11s and llb. Reduction of this dibromide with lithium in tert-butanol gave hydrocarbon which was tentatively assigned structure 12 based on lH NMR spectrum. This structural assignment was unambigeously supported by X-ray structural analysis. The first (to our knowledge) sttucture of spirohexene compound is outlined in figure 1.
K.A. Ltnm et al.
lH and 13C NMR study of the second fraction indicated that it was 1:l mixtme of compound llaand dibromide 13. Formation ofcompound13 could be accounted for by allylic mode of coupling of intermediate bromide 14inpresense of MeLi. Such mcde of coupting was found in the case of l-~m~me~y~~yci~ bt~te.ne.~~Thus it was found that narmngement of dibmmide 7 proceeded in a selective manner to yield prrt ducts, that could be associated only with formation of intermediate 14.
In conclusion, we have found a new type of reaction of cyclopmpane gem-dibnxnides in the presence of methyllithium. This reaction is characteristic for aiaqu.lanes gernditromides and includes rearrangement of dibmmoqimpentane fiagment into 2-bromt+ l-(IxxxnomethyQcyclobutene one as a key step. Such rearrangement could be hardly associated with ~~~~~n~d or cyclic interme&q. While mechanistic aspects of thii xeaction remain to be clarified,~3 it opens a new useful synthetic approach to compounds with bromocyclobutenyl and cyclobutenyl moieties.
Unusual rearrangement of triangulane gem-dibromides
9981
Experimental Section. General. ‘H and 13C NMR spectra were recorded in CDCl3 GC analysis was carried out with a 3000 x 3 mm column packed with SE-30 on Jnerton NAW phase. Mass spectra were obtained at 12 eV. l,l-Dibromospiropentane (l), 7,7-dibromodispiro[2.2.l]heptane (3). and l,l-dibromodispiro[2.2.1]heptane (7) were prepared by cycloaddition of dibromocarbene to cortesponding olefiis according to a literature procedure.1o Reaction of Dibromide 3 with Metbylithium. To a magnetically sthred solution of dibromide 3 (14 mmol. 3.53 g) in dry ether (10 mL), methyllithium (19 mmol, 16 nL of 1.2 N solution in ether) was added dropwise over 0.5 h at -50 - -55 OC under argon. The reaction mixture was then allowed to warm to 0 OC and quenched with water. The organic layer was separated, washed with water and dried with MgSO4 The solvent was evaporated and fractional distillation of the residue gave allene 4 and dibromide 5. Bis(cyclopropylidene)methane (4)14 was obtained in 21% yield: *H NMR 6 1.48 (s); 13C NMR 6 7.38 (4 C). 80.98 (2 C), 176.57 (1 C). 2-Bromo-1-(l-bromocyclopropyl)cyclobutene
(5): 1.7 g. 48%; bp 54-56 OC (3 mm); lH NMR (250
MHz) 6 1.29 (m, 2 H), 1.38 (m, 2 H). 2.60 (m, 2 H), 2.64 (m, 2 H); 13C NMR 6 16.39 (t. J = 166 Hx. 2 C), 25.67 (s. 1 C), 30.80 (t, J = 143 Hz, 1 C), 33.67 (t, J = 143 Hz, 1 C), 108.47(s, 1 C), 146.43 (s, 1 C); Anal. Calcd for C7H8Br2: C, 33.36; H, 3.20. Found: C, 33.22; H. 3.23. When this reaction was carried out at -5 - -7 OC allene 4 was isolated in 60 46 yield; dibromide 5 was obtained in 10% yield and new product - bromoiodide 6 was isolated in 11% yield 1-(1-Bromocyclopropyl)-2-iodocyclobutene
(6): bp 62 - 63 OC (3 mm); nD20 1.6053; *H NMR
(250 MHz) 6 1.28 (m, 2 H), 1.36 (m, 2 H), 2.65 (m, 2 H); 2.80 (m, 2 H); 13C NMR 6 15.92 (2 C). 26.66, 34.43, 35.01, 82.08, 153.94. MS (m/e): 300,298 (M+), 220, 173. 171.92 (base), 91. When the same reaction was carried out at +5 - +8.OC only allene 4 and iodide 6 were obtained in 19% and 33% yield, respectively. 1,2-Bis(2-bromo-1-cyclobutenyl)ethane (8). Reaction of dibromospiropentane 1 with methyllithium was carried out in accord with the procedure given above. Allene 2. which was produced in 25% yield, and the solvent were distilled into a cold to -78 OC trap. Distillation of the residue gave dibromide (8) in 1.16 g, 27% yield; bp 91-94 OC (2 mm); lH NMR (250 MHz) 6 2.21 (br s, 4 H), 2.51 (m, 4 H), 2.71 (m. 4 H); 13C NMR 8 25.47 (t, J = 129 Hz), 30.49 (t, J = 142 Hz), 35.08 (t. J = 142 Hz), 108.52 (s), 147.40 (s). Anal. Calcd for ClOHl2Br2: C, 41.13; H, 4.14. Found: C, 41.38; H. 4.02. Reaction of l,l-Dibromodispiro[2.2.l]heptane (7) with methyllithium was carried out in accord with the procedure given above. The solvent was evaporated and column chromatography of the residue gave: fraction 1 - dibromide lla, and fraction 2 - 1:l mixture of dibromides lla and 13. 1,2-Bis(2-bromospirohex-4-ene-4-yl)ethane
(lla):
1.03 g, 43%; mp 37 OC; lH NMR (250 MHz) 6
9982
K. A. LUKINet al.
0.77 (s, 8 H), 2.0 (s, 4 I-l), 2.80 (s, 4 I-I); 13C NMR 6 6.63 (t, J = 162 Hz). 22.64 (t, J = 130 Hz), 30.94 (s). 45.11 (t, J = 142 Hz), 104.34 (s), 149.48 (s). Anal. Calcd for Cl4Hl6Br2: C, 48.86; H, 4.69. Found: C, 49.03; H, 4.42. 5-Bromo-4-[(5-bromo-4-methylenespirobex-S-yl)methyl]spirohex-4-ene
(13): lH NMR (250
MHz) 6 0.79 (s, 4 H), 0.8 - 1.0 (m, 4 I-I), 2.7 - 2.9 (m, 6 I-l), 4.58 (d, J = 1.75 Hz, 1 I-I), 4.97 (d, J = 175 Hz, 1 II); 13C NMR 6 7.02, 7.36, 14.86 (2 C), 31.48, 31.91, 40.48, 45.46, 46.46, 58.95, 101.49, 111.00, 147.51, 162.28. For a mixture of bromides lla and 13 anal. calcd for Cl4Hl6Br2: C. 48.86, II, 4.69. Found: C. 48.49; H, 4.68. Reduction of Dibromides 8 and lla with Lithium in tert-Butanol. Preparation of Hydra. carbons 9 and 12. To a stirred solution of dibromide (8 mmol) and tert-butanol(3.8 mL. 40 mmol) in dry TI-IF (25 mL), lithium tunings (0.35 g, 50 mmol) were added portionwise, allowing gentle boiling of reaction mixture. After 3 h pentane (25 mL) and water (50 rnL) were added. Permute layer was washed with water (3 x 50 m.L), dried with MgS04 and the solvent was evaporated. Olefins 9 and I2 were isolated by distillation. l&Bis(l-cyclobutenyI)ethane
(9) was isolated in 0.74 g, 69% yield: bp 75-76 OC (20 mm). lH NMR
was in accord with literature data12 If-Bis(spirohex-4.ene-4.yl)ethane
(12) was isolated in 78% yield: mp 43 OC; lH NMR (250 MHz)
6 0.7 (s, 8 I-I), 1.93 (s, 4 I-I), 2.49 (s, 4 I-Q, 5.78 (s. 2 H); 13C NMR 6 6.62, 23.33, 30.39, 37.25, 123.80, 152.48.
X-ray Structural Analysis of l&Bis(spirohex-4-ene-4.yl)ethane
(12).
Data collection was performed from the transparent prism-shape crystal with Siemens P3/PC four circle diffractometer using graphite monochromatized MO K, radiation. Hydrocarbon 12. Monoclinic crystalls. Cell parameters at -90 OC: a = 9X5(6) A; b = 5.373(3) & c = 11.981(6) A; a = 900; p = 112.09(4)O; y= 900. Vol = 553.8 (1.1) A3. Unit contents: Cl4Hl8, Z = 2. Density: 1.117 g/cm3 . Space group: P2( 1)/C. Intensity data were collected on 1364 reflections (871 with I > 4s). Final R = 0.050; Rw = 0.049.The structure has been solved by direct method and refmed by full-matriz least squares anisotropically. All H-atoms were obtained from the difference Fourier map andrefined isotropically. Programm SI-IRLX PLUS (PC) version was used in all calculations. Structural data am collected in Tables 1 - 5. Table 1. Atomic coordinates (~1~) and temperature factors (k103). Atom C(1) C(3) C(5) C(7) ______
x
Y
Z
9469(2) 3982(4) 10068(2) 8649(3) 2559(5) 7817(2) 7218(2) 943(4) 8579(2) 5775(3) 1152(5) 8868(2)
U*
Atom
25(l) 31(l) 27(l) 33(l)
C(2) C(4) C(6)
x
Y
8565(2) 2705(4) 7317(3) 701(5) 6874(3) -1007(5)
z 8912(2) 7319(2) 9338(2)
*Equivalent isotropic U defined as one thii of the trace of the orthogonal&d U(ij) tensor.
U* 24(l) 33(l) 32(l)
Unusual rearrangement of triangulane gem-dibromides
9983
Table 2. Bond L.enths (A). C(l)-C(2) C(l)-C(la) C(2)-C(3)
1.490(3) 1.522(S) 1.344(3)
C(2)-C(5) C(3)-C(4) C(4)-C(5)
1.498(3) 1.52X3) 1.552(3)
C(5)-C(6) C(S)-C(7) C(6)-C(7)
1.499(4) 1.509(4) 1.507(4)
Table 3. Bond Angles (deg). C(2)-C(l)-C(la) C(4)-C(5)-C(6) C(3)-C(2)-C(5) C(6)-C(S)-C(7) C(2)-C(5)-C(4)
113.1(2) 129.5(2) 93.0(2) 60.1(2) 87.9(2)
C(2)-C(5)-C(6) C(l)-C(2)-C(5) C(4)-C(5)-C(7) C(3)-C(4)-C(5) C(5)-C(7)-C(6)
128.9(2) 131.3(2) 127.7(2) 84.3(2) 59.6(2)
C(l)-C(2)-C(3) C(2)-C(5)-C(7) C(2)-C(3)-C(4) C(5)-C(6)-C(7)
135.6(2) 128.1(2) 94.8(2) 60.3(2)
Table 4. Anisotropic Temperature Factors (A2 x 105. Atom
Ull
U22
u33
C(1) C(3) C(5) C(7)
28(l) 33(l) 25(l) 26(l)
27(l) 38(l) 33(l) 42(l)
21(l) 28(l) 23(l) 34(l)
U23 l(1) -5(l) -2(l) 4(l)
U13
U16
Atom Ull
U22
U33
U23
U13
U16
11(l) 16(l) 11(l) 14(l)
l(1) -6(l) O(1) O(1)
C(2) 25(l) C(4) 33(l) C(6) 32(l)
26(l) 42(l) 30(l)
22(l) 25(l) 34(l)
-l(l) -6(l) 5(l)
11(l) l(1) 13(l) -4(l) 12(l) -2(l)
Table 5. Hydrogen Coordinates (~10~) and Temperature Factors (A2 x 102).
Atom H(11) H(3) ~(42) H(62) H(72)
X
1005 934 638 752 577
Y 279 350 134 -101 253
z 1062 746 662 1019 944
U
Atom
X
Y
3 4 3 4 4
H(12) H(41) H(61) H(71)
874 764 657 480
474 -98 -267 84
Z
1042 716 900 826
U 3 2 3 4
K. A. LUKINet al.
References and Notes 1. Hopf, H. In Patai, S. Ed.; The Chemistry of Kerenes, AlIenes and Related Compounds, Part 2; Wiley: New York, 1980; Chapter 2. 2. Kirmse., W. Carbene Chemistry; Academic: New York, 1971,302 p. 3. For examples, see: a) Nilsen, N.O.; Skattebol, L.; Baird, MS.; Buxton, S.R.; Slowey, P.D. Tetrahedron L.ett. 1984,25, 2887-2890, b) Semmler, K.; Szeimies, G.; Belzner, J. J. Am. Chem. Sot. 1985,107, 6410-6411. 4. For examples, see: a) Moor, W.R.; Ward, H.R.; Menit, R.F. J. Am. Chem. Sot. 1961,83, 2019-2020; b) Brown, D.W.; Hengrick, ME.; Jones, M. Tetrahedron Lett. 19’73,3951-3954; c) Scattebol, L.; Stenstrom, Y.; Stjema. M.-B. Acra Chem. Stand. 1988,B42.475-483. 5. Scattebol, L. Chem. and Industry 1962,2146. 6. Zefirov, N.S.; Kozhushkov. S.I.; Kuznetzova, T.S.; Kokoreva, O.V.; Lukin. K.A.; Ugrak. B.I.; Tratch, S.S. J. Am. Chem. Sot. 1990.112. 7702-7707. 7. Lukin, K.A.; Kozhushkov. S.I.; Andrievski. A.A.; Ugrak, B.I.; Zefuov. N.S. J. Org. Chem. 1991,56. 6176-6179. 8. Fitjer, L.; Conia, J.M. Angew. Chem. 1973,85, 832-833. 9. Barlet. R.; Vincens, M. Tetrahedron 1977.33, 1291-1302. 10. Lukin. K.A.; Zefirov. N.S. Zh. Org. Khim. 1987,23, 2548-2552. 11. lH NMR of a crude product indicated - 10% of admixture that was tentatively assigned structure of 2brome l-[( 1-bmmo-2-methylenecyclobutyl)methyl]cyclobutene. However, this compound decomposed during attempted isolation by distillation or column chromatography. 12. Shea, K.J.; Wise, S. J. Org. C&m. 1978,43, 2710-2711. 13. No changes in lH NMR of dibromospiropentane were observed after 12 h stirring with a solution of dry lithium bromide in ether, Compound 8 was the main product of the reaction when butyllithium was used instead of methyllithium at -50 PC. However. I-bromo-1-lithiospiropentane was obtained and characterized by nucleophilic additions to aldehydes when this reaction was carried out at -110 PC (unpublished results), 14. a) Kopp, R.; Hanack, M. Angew. Chem. Internat. Edit. 1975,X4.821-822.b) Eckert-Maksic. M.; Zollner, S.; Gothling, W.; Boese. R.; Macsimovic, L.; Machinek, R.; De Meijere, A. Chem. Ber. 1991. 124, 1591.