Nov. 5 , 1962
CORIMIJNICATIONS TO THE EDITOR
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propyl ring is not substituted.5 The coinplex proton magnetic spectra of the two compounds are very similar, differing only in slight shifts of peak positions and in relative intensities. These n.ii1.r. spectra have not yielded to analysis, perhaps because several stereoisomers are present. However, protons in a t least eight different environments are found, consistent with the nortricyclene structure (16) Kational Aniline Research Fellow, 1961-1962 and inconsistent with alternative pi-complex forDEPARTMESTOF CHEMISTRY OF BUFFALO PETERT LANSBURY mulations. UNIVERSITY YORK JAMES G COLSON~” Upon treatment with water or bases the comBUFFALO14, SEW pounds undergo a remarkable fragmentation reRECEIVED AUGUST27, 1962 action,€with the reformation of bicycloheptadiene and a tin-containing fragment. This reaction TIN TETRAHALIDE ADDUCTS OF may be explained as a delta-elimination brought BICYCLOHEPTADIENE AND THEIR about by attack of the base at tin FRAGMENTATION’
value in the synthesis of heterocyclic rings. I t should be pointed out that insertion products such as I1 may have been formed in other Beckmann or Schmidt reactions and were inadvertently missed since they would remain in the oft-discarded diluted acidic solution from which the usual neutral products are removed by filtration or extraction.
Sir: r iQ Slthough olefins generally are known to be attacked by electrophilic reagents, few studies have been published on the interaction of olefins with strong Lewis acids other than boron hydrides.2 Recently it has shown that BC13 and C6H5BC12will J I\ add t o several reactive olefins, including bicycloBSnX3 heptadiene. We now wish to report the addition of SnC1, and xo SnBr, to bicycloheptadiene (I) to yield crystalline 1: 1 adducts, which like the boron halide adductsY The fragmentation is quantitative and was used are formulated as substituted nortricyclenes (11). for approximate analysis of the compounds, sufficient to show that they are 1:1 adducts. In a typical hydrolysis, the SnC&adduct gave bicycloheptadiene, 25.9; Sn, 35.8; C1, 38.0 (calcd. for C7HI0SnCl4; bicycloheptadiene, 26.5; Sn, 33.4; C1, 40.0). The SnBr, adduct gave bicycloheptaI I1 diene, 16.3; Sn, 19.6; Br, 60 (calcd. for CwHloThese products presumably arise through homo- SnBr4, bicycloheptadiene, 17.6; Sn, 22.3; Br, conjugative addition of the type described by 60.1). Conventional combustion analyses were Winstein and Shatavsky. The compounds are impractical because of the instability of the comprepared simply by mixing the reactants in ap- pounds. proximately equimolar proportion in dry isopenThe adducts are stable pure or under hydrotane a t 0’ and allowing the solution to stand. The carbons a t 0’ or below, but a t room temperature colorless crystals which form may be recrystal- or in contact with polar solvents they decompose lized from fresh isopentane; m.p. for C7HloSnC11, with the formation of tarry masses apparently 60.5-61.5’; for C7HloSnBr,,58-59’. containing polymerized material It seems not The infrared spectra of the two compounds pro- unlikely that similar adducts may be formed vide strong support for the nortricyclene structure. during the polymerization of diolefins by SnCl?. Both compounds have strong bands a t 3070 and 1020 cm.-l, which are diagnostic for the cyclo- Experiments are under way with other Lewis acids and olefins to determine the generality of propane ring in nortricyclene~.~-4 band also the addition reaction. Preliminary results indiappears in the 800-818 ern.-' region in both compounds, consistent with the fact that the cyclo- cate that GeBr4 and C6H5SnC&form adducts with bicycloheptadiene, but that SnI,, Sic14 and ((26( 1 ) This research was supported by t h e directorate of Chemical H5)*SnC12 do not. Sciences, Air Force Office of Scientific Research, under grant KO.AF-
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AFOSR-62.244. (2) H. C . Brown, “Hydroboration,” W . A. Benjamin, Inc., 9 e w York, pi. Y . , 1902 ( 3 ) F. Joy and F . M. Lappert, Proc. Chepn Soc. ( L o n d o n ) , 353 (1960) (4) S. Winstein and 42. Shatavsky, Chem. arid I n d . , 56 (1986). ( 3 ) G. E. Pollard, Spectuockim. Acla, 18, 887 (1962). Cf. J. D. Roberts, E. R. Trumhull, W. Bennett and R.Armstrong, J . A m . C k e m . Soc., 74, 3116 (1950); E . R. Lippincott, ibid., 73, 2001 (1951).
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DEPARTMENT OF CHEMISTRY OF WISCONSIN FREDRIC M. RABEL UNIVERSITY 6, WISCOSSIN ROBERTWEST MADISON RECEIVED SEPTEMBER i , 1962 (6) C. A . Grob and W. Baumann, H e l u . C h i m . A c t a , 38, 594 (1955); C . A. Groh, “Fragmentation in Solvolysis Reactions,“ in “Theoretical Organic Chemistry” (papers presented a t t h e Kekule Symposium), Butterworths, London, 1959, p p , 114-126.
