STEREOCHEMISTRY OF NUCLEOPHILIC-ADDITION TO SEVERAL RIGID, STERICALLY UNBIASED 7-NORBORNANONES

A stereochemical investigation is reported of the reactions of lithium aluminum hydride (LAH) and of methyllithium with three sterically unbiased, rigid ketones: tetracyclo[7.4.0.0(2,7).0(6,10)]trideca-3,12-dien-8-one (2), pentacyclo[6.5.0.0(4,12).0(5,10).0(9,13)]tridecan-11-one (3), and pentacyclo[6.5.0.0(4,12).0(5,10).0(9,13)]trideca-2,6-dien-11-one (4). Various proton NMR techniques were brought to bear upon the dual problems of characterization and analysis of the mixtures of epimeric alcohols obtained. The results can be interpreted in terms of transition-state hyperconjugation. A comparison with literature data on other endo-substituted 7-norbornanones points up the need, in studies of electronically controlled face selection, for probes that not only have sterically equivalent faces but are also conformationally rigid.