Stereocontrolled synthesis of [3.1.0]bicyclohexanones by cyclopropanation of enones with benzylidene sulfuranes

Bicyclo[3.1.0]hexanones bearing an aryl group on the cyclopropane ring are stereoselectively prepared on reaction of the corresponding benzylidene sulfuranes with cyclopentenones. The synthesis of compounds bearing geminal phenyl and methyl groups on the cyclopropane ring proves to be possible because the corresponding sulfonium salt, inaccessible until now, is now available.