STEREOSELECTIVITIES OF NUCLEOPHILIC ADDITIONS TO CYCLOHEPTANONES - EXPERIMENTAL AND THEORETICAL-STUDIES AND GENERAL-PURPOSE FORCE-FIELD FORTHE PREDICTION OF NUCLEOPHILIC-ADDITION STEREOSELECTIVITIES

The selectivities of nucleophilic additions of ethyl, vinyl, and ethyn yllithium and Grignard reagents to a 2-(3'-phenylpropyl)cycloheptanone were investigated experimentally. In all cases, cis-cycloheptanol was formed preferentially (40:1-6:1). Theoretical studies were performed on the stereoselectivities of nucleophilic additions of hydride and et hynyllithium reagents to cycloheptanones. An empirical force field for transition states of hydride and ethynyl reagents was used for transi tion-state geometries and conformational searches. Quantum mechanical calculations on HLi addition to cycloheptanones were compared to the c orresponding cyclohexanone calculations. These results show that the f ormation of 2-alkyl-substituted cis-cycloheptanols is preferred for al l nucleophiles studied as a result of torsional and steric effects in the transition states of these reactions.