The reaction of 2-methylnorborn-2-ene with N-bromosuccinimide produced exo-3bromo-2-methylenenorbornane and 2-methyl-3-bromonortricyclene in a 3 : 1 ratio. No 2-bromomethyl-norborn-2-ene was found. Most of the unreacted olefin was found to be isomerized to 2methylenenorbornane.The hydrolysis of 2-methyl-3-bromo-nortricyclene with silver acetate in a 50 yo mixture of acetone and water afforded the corresponding alcohol and acetate. Exo-3-bromo-2-methylenenorbornane on similar treatment gave the exo-3-hydroxy-2-methylene-norbornane and 2-hydroxymethyl-norbornane and 2-hydroxymethyl-norborn-2-ene and their corresponding acetates in a 3: 2 ratio.An ionic rather than a radical mechanism is proposed for the bromination reaction. In the solvolysis reactions of the resulting bromides the nature of the ionic intermediates is discussed.Introduction, -The behaviour of N-bromosuccinimide (NBS) as a brominating agent towards bridged bicyclic olefins is capricious. When the allylic C-H bond lies in the nodal plane of the double bond, reactivity is usually directed towards the homoallylic position or the double bond itself [Z]. When an allylic position is available, bromination is thought to proceed via allylic radicals which subsequently give the corresponding endocyclic allylic bromides (31.As 2-methylnorborn-2-ene contains both these structural elements, its reactivity is of crucial interest. Furthermore, the properties of the bromides obtained relate to the problem of the nature of bridged cations.Results. -2-Methylnorborn-2-ene (I) and N-bromosuccinimide were allowed to react in boiling carbontetrachloride containing benzoyl peroxide. The resulting products were identified as exo-3-bromo-2-methylene-norbornane (II), 3-bromo-%methylnortricyclene (111) and 2-methylenenorbornane (IV). The structures of I1 and 111 were assigned from a consideration of their NMR. and IR. spectra. The exo assignment of the bromine at C-3 in I1 was made on the basis of the magnitude of the coupling constant exhibited for C-3-H, (3J N 1.8 Hz) ; a larger value (ca. 4 Hz) would l) Address inquiries to the
Because of the presence of the bromine atom in cis-l-(2-bromo-3-phenanthryl)-Z-(Z-naphthyl)e-thylene (XI), the upfield shift of H, (Ha3) is much larger than in the corresponding unsubstituted cis-1, 2-diarylethylene.We acknowledge the fact tlydt other co-workers have made similar observations in the course of the last few years. The financial support of the 'Fonds de la Recherche Fondamentale Collective' is gratefully acknowledged. One of us (J.J.R.) exprcsses his gratitude t o the 'Znstitut pour I'Encouragewent de la Recherche Scientafaque duns l'lndustvie el I'Agrirulture' for the award of a fellowship.
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