Cyclopropanes via an efficient 3-exo trig radical cyclisation reaction

Abstract

The sequential alkylation, oxidn. and bromination of S)-carvone gave 7-bromo-4,7-dimethyl[2.2.2]bicyclooct-5-en-2-one derivs. I (R = Ph, $4-MeC_6H_4$, $4-MeOH_6H_4$, $2-MeOC_6H_4$, $C^0CPh$) and a 1:1 mixt. of isomeric 4-bromo-2, 5-dimethyl[3.2.1]bicyclooct-7-en-2-one derivs. II (same R). The 3-exo trig radical cyclization, i.e., homoallylic (cyclopropyl)methyl radical cyclization, of I and II gave tricyclooctanes III (same R).