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1,3-Dibromoadamantanes reacted with glycols in the presence of sodium glycolate to give novel unsaturated bicyclo[3.3.1]nonane derivatives and 1,3-disubstituted adamantanes. X = Cl, Br, MeO, MeS, H 2 N, MeNH, Me 2 N.Fragmentation of some 1,3-disubstituted adamantanes through intermediate formation of stabilized 3-substituted 7-methylidenebicyclo[3.3.1]non-3-yl cations was reported in [1][2][3][4][5][6][7]; in the presence of water the latter were converted into 7-methylidenebicyclo-[3.3.1]non-3-one (Scheme 1). Presumably, in strongly basic medium such carbenium ions can be stabilized via elimination of proton with formation of double C=C bond.We previously found [8] that 1,3-dibromoadamantane (I) in ethylene glycol at 200°C in the presence of a strong base is converted into a mixture of 2-(7-methylidenebicyclo[3.3.1]non-2-en-3-yloxy)ethanol (II) and 7-methylidenespiro[bicyclo[3.3.1]nonane-3,2′-[1,3]dioxolane] (III). More detailed analysis of the product mixture allowed us to reveal 10-12% of 2,2′-(adamantane-1,3-diybisoxy)diethanol (IV). 1,3-Dibromo-5,7-dimethyladamantane (VI) reacted in a similar way (Scheme 2).The products were isolated from the reaction mixture by selective extraction and subsequent vacuum distillation or recrystallization from appropriate solvent.As might be expected [9], vinyl ether II upon distillation or heating to 100°C, as well as during chromatography on silica gel, is quantitatively converted into spiro dioxolane III. Protection of the hydroxy group by esterification made it possible to isolate by vacuum distillation 2-(7-methylidenebicyclo-[3.3.1]non-2-en-3-yloxy)ethyl acetate (Va); the corresponding p-nitrobenzoate Vb was isolated by fractional recrystallization from methanol. Compounds IVa and IXa were isolated and characterized as p-nitrobenzoates IVb and IXb (Scheme 2).The structure of the products obtained by reactions of 1,3-dibromoadamantanes I and VI with ethylene glycol suggests the following reaction mechanism. 1,3-Dibromoadamantane I or VI in polar medium gives rise to 3-bromoadamantan-1-yl cation which takes up ethylene glycol molecule to produce intermediate A. Heterolytic dissociation of the C-Br bond in A generates cation B which undergoes Grob fragmentation with formation of carbenium ion C. The latter can be stabilized according to two pathways. Intramolecular proton abstraction from the α-carbon

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2002 bridged compounds bridged compounds Q 0060 13 -093 Cyclization of 7-Methylene-3-[2-(4-nitrobenzoyloxy)ethoxy]bicyclo[3.3.1]non-2-ene in the Presence of Acids. -The title compound (I) is unstable in the presence of traces of acid. It is rapidly converted into the corresponding adamantane derivatives (III), (V), and (VI) in nucleophilic solvents or dry HCl. -(SKOMOROKHOV, M. YU.; KLIMOCHKIN, YU. N.; Russ.