The relative importance of addition and reduction, as well as the syn:anti selectivity of those processes, were determined for the reactions of five Grignard reagents with norbornen-7-one. Reduction is important or dominant in the reactions of Grignard reagents having β-hydrogen and there is a strong preference for the hydride transfer to occur from the syn face of the carbonyl group. Addition shows the analogous stereochemical preference with higher selectivity than reduction.
Alkyllithium reagents (RLi: R = methyl, n-butyl, t-butyl) add to norbornen-7-one either without stereochemical preference (R = n-butyl) or with syn attack favored. This addition selectivity is qualitatively the same as that shown by corresponding alkylmagnesium reagents but competition from reduction is much less important in the case of alkyllithium reagents.Phenyllithium and vinyllithium add preferentially from the anti face, although the corresponding Grignard reagents add selectively from the syn face. Possible causes of the stereoselectivities are considered. Solvent effects on the stereochemistry of addition are small.