Palladium dialkynylation

Alkynylpalladium reagents can be useful intermediates in the synthesis of diynes by catalytic coupling reactions since the dialkynyl-palladium complex (PPh3)2Pd((3sCR)2 (9) has been shown to easily produce the corresponding diyne on reductive elimination. ... 

The other organometallic compounds, such as alkynylcoppers, alkenylzincs, and alkenylzirconocenes, have also been utilized for the tran -selective couphng reaction of 1,1-dihaloalkenes (Scheme 4). The monoalkynylation of 1,1-dichloroethylene in the presence of palladium and copper catalysts is troublesome. Since dialkynylation is not easily suppressed, an excess amount of the substrate, 1,1-dichloroethylene, is required to produce the desired product. 

Masai H, Sonogashira K, Hagihara N (1971) Electronic spectra of square-planar bis(tertiary phosphine)dialkynyl complexes of nickel(II), palladium(II), and platinum(II). Bull Chem Soc Jpn 44(8) 2226-2230... 

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