Solutions of carbenoids 4a and 1 la were prepared by the reaction of alkyllithiums with dihalocyclopropanes 1. Carbenoid 4a had limited stability at-80" but could be trapped by carbonation which gave 2 in low yield and by protonation which gave 4b in high yield. Bicyclobutane 5 was the major product of thermal decomposition of 4a. Carbenoid lla was more stable at-80" as evidenced by reactions with HtO, DnO, and benzophenone. Thermal ...
