The reaction of geraniol with different lithium carbenoids generated from n-BuLi and the corresponding dihaloalkane has been evaluated. The reaction occurs in a chemo and stereoselective manner, which is consistent with a directing effect from the oxygen of the allylic moiety. Furthermore, a set of polyenes containing allylic hydroxyl or ether groups were chemoselectively and stereoselectively converted into the corresponding gem-dimethylcyclopropanes in one single step in moderate to good yields mediated by a lithium carbenoid generated in situ by the reaction of n-BuLi and 2,2-dibromopropane.