Ring Expansion of Bicyclic gem-Dihalo- and Monohalocyclopropanes

Publisher Website
Google Scholar
Abstract
Some bicyclic gem-dichlorocyclopropanes (Ia through Id) and gem-chlorofluorocyclopropanes (IIa through IId) were prepared by the addition of dichloro- and chlorofluorocarbene, respectively, to the appropriate cyclic olefins. The reduction of these dihalocyclopropanes with tri-n-butyltin hydride gave the corresponding monochloro- (IIIa through IIId) or monofluorocyclopropanes (IVa through IVd) in fairly good yields. When treated with an excess of hot quinoline, the endo-chloro isomers of IIa, IIb, IId, IIIa, IIIb, and IIId were converted to their ring expansion products, whereas their exo-chloro isomers were recovered unchanged. In contrast, the exo-chloro isomers of IIe and IIIc decomposed more readily than their endo-chloro isomers under similar conditions. These results were discussed on the concept of a concerted disrotatory process.