Fig. 4. Carbene insertions into BCBs to give halogenated BCPs.

A Insertion of dichlorocarbene into bicyclobutanes. B Insertion of bromofluorocarbenes radicals into bicyclobutanes and the selective debromination to give monofluorinated bicyclopentanes. C Insertion of difluorocarbenes into bicyclobutanes along with functional group tolerance and downstream targets from these products. D Mechanistic investigations into the carbene insertion reaction by Anderson and co-workers which support a stepwise insertion mechanism. EDA ethylenediamine, TMS trimethylsilyl, Boc tert-butoxycarbonyl.