Face selectivity in the reactions of Grignard reagents with 5-substituted-2-dicyanomethyleneadamantanes

Abstract

Reactions of 5-substituted-2-dicyanomethyleneadamantanes (4-Z) with benzylmagnesium bromide (C₆H₅CH₂MgBr) or alkylmagnesium halides (RMgX) generated the 1,4-addition (5-Z (R)) and/or the hydrogenation (5-Z (H)) products. A variety of substituents X were used: hydro, fluoro, chloro, bromo and phenyl groups. The generation of the different isomeric products from the zu-face or en-face by the transfer of the benzyl or alkyl groups, or the hydride from the Grignard reagents is discussed in terms of the electrostatic field influence and the steric hindrance between the Grignard reagents and the substrate 4-Z. Reactions of 4-Br or 4-Ph with phenylmagnesium bromide generated 1,2-addition products 6-Br, 7-Br or 8-Ph when the intermediate A was added to dry methanol or to dilute ice-cold hydrochloric acid solution.