1-halocyclopropenes and propargylic halides from the reaction of trihalocyclopropanes with methyl lithium

1,1,2-Trihalocyclopropanes (halogen = chlorine or bromine) undergo 1,2-dehalogenation on reaction with methyl lithium, and in a number of cases the product is a 1-halocyclopropene. In the reactions of (20, X = Br, Cl) and (25) a rearrangement occurs even at low temperatures and propargylic halides are isolated, while (16) is converted to 2-chlorocyclohex-2-enylidene which may be trapped by furan.