A convenient preparation of mono- or gem-di-halogenoalkanes from α-sulfonyl carbanions and halogenolithiocarbenoids.

Article abstract of DOI:10.1016/0022-328X(89)85159-9

Various α-sulfonyl carbanions have been shown to react at low temperature with di- or tri-halogenolithiocarbenoids, to give 1-mono- or 1,1-di-halogenoalkanes.Bromocarbenoids gave better results than their chloro-analogues.Reaction of dibromolithiomethane with α-lithiated sulfones gives a high yield of vinylic bromides, the stereochemistry of which is cleanly E.Evidence is presented that the carbenoid itself is responsible for the reaction, and is not first converted into the corresponding carbene.