SYNTHESIS AND STEREOMUTATION OF 5-SUBSTITUTED BICYCLO[2.1.0]PENTANES

A synthetic route has been devised to provide access to a number of 5-substituted bicyclo[2.1.0] pentanes, including those bearing π-acceptor substituents (i.e., exo- and endo-5-cyanobicyclo[2.1.0]pentane and exo- and enr/o-5-carbomethoxybicyclo[ 2.1.0]pentane). The thermochemically induced stereomutation of these isomeric compounds was studied, and their activation parameters were contrasted with those of bicyclopentanes bearing π-donor (e.g., OPNB) substituents. The findings are consistent with substituent effects involving a resonance interaction that influences the stability of the ground-state molecules, and/or an effect acting at the transition state (or biradical state) which involves the electronegativity of the attached substituent. © 1979, American Chemical Society. All rights reserved.