Science of Synthesis

Hirsch, A.; Vostrowsky, O., Science of Synthesis, (2008) 43, 99.

1,1-Dihaloalkenes are not used merely to generate alkynes through Fritsch–Buttenberg–Wiechell rearrangements (Section ‌43.1.1.1.17‌), they also provide a convergent route to triynes and higher oligoynes through the assembly of two short monoynyl or oligoynyl intermediates.[‌326‌] Here the critical step is the palladium-catalyzed monoalkynylation of a 1,1-dibromo- or 1,1-dichloroalkene.[‌329‌,‌330‌] For example, the enynes ‌198‌, which are available from the corresponding aldehydes via the Corey–Fuchs technique,[‌272‌] are monoalkynylated with alkynyl zinc derivatives ‌199‌ in the presence of a base and, under the influence of a palladium catalyst, undergo Negishi coupling to yield the polyynes ‌200‌ (‌Scheme 58‌).[‌326‌]

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References