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43.6.1.4.5.2 Variation 2: Corey–Fuchs Modification

DOI: 10.1055/sos-SD-043-00304

Griesbeck, A. G.; Soldevilla, A.Science of Synthesis, (200843381.

Terminal alkynes are accessible from 1,1-dibromoalkenes via halogenmetal exchange and subsequent metal halide elimination induced by strong bases {see Science of Synthesis, Vol.25 [Aldehydes (Section 25.1.10.6.2)]}. This process was initially demonstrated by Corey and Fuchs for gem-dibromostyrenes (Scheme 45).[‌147‌] Benzylic alcohols can be converted into alkynes in a one-pot conversion using manganese dioxide to effect a tandem oxidation process, followed by CoreyFuchs reaction.[‌148‌] For alkenation, a mixture of triphenylphosphine and carbon tetrabromide can be used, which generates the dibromo ylide 83 in situ, or the dibromomethyl phosphonium ylide may be treated with alkoxide bases.[‌149‌] Treatment of the ylide with an organolithium affords the terminal alkyne 84.

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