Hydro-halo-elimination

Dehydrohalogenation of Alkyl Halides Hydro-halo-elimination... 

The introduction of 1,2-bromochlorocyclopropene (27) by Billups as a synthon for cycloproparenes constituted a major achievement and made a large number of previously unaccessiblecycloproparenes, lacking substituents at Cl, available. The cyclopropene 27 is labile and decomposes at room temperature, but nevertheless undergoes addition to a variety of dienes around -20 °C. In some cases reaction times of several days or even weeks are necessary in order to obtain complete conversion. The stereoselectivity for the addition of 27 to open-chain dienes is usually exo, as in the case of the tetrahalogenocyclopropenes. Bis-(hydro,halo-geno)elimination is carried out with r-BuOK in THF, as in the case of the adducts of tetrahalogenocyclopropenes. 

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