Diphenylacetylene, Sonogashira reaction

The Sonogashira reaction allows for the direct cross-coupling of terminal alkynes with aryl halides under mild conditions through use of catalytic bis(triphenylphosphine)-palladium dichloride and Cul as the co-catalyst in the presence of an aliphatic amine. The formation of diphenylacetylene exemplifies the original Sonogashira reaction conditions ... 

Scheme 8.5 Alkyne metathesis reactions of polymer 35 prepared from the (a) Sonogashira condition and (b) hexacycle 36 and diphenylacetylene [35].

The reaction can be combined with Sonogashira coupling to give o, o -dialky-lated diphenylacetylenes [11]. Pd-catalyzed reaction of iodobenzene, ethyl bromide, and phenylacetylene (36) afforded 2,6-diethyldiphenylacetylene 37 in 78 % yield with remarkable chemoselectivity. In this reaction, Cul as a cocatalyst was not used. The direct Sonogashira coupling of iodobenzene with phenylacetylene (36) was suppressed by slow addition of excess ethyl bromide and phenylacetylene at room temperature. 

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