Nickel-Catalyzed Cross-Coupling Reaction of Allyl Halides with Alkynyltins

Article abstract of DOI:10.1021/jo00123a006

A cross-coupling reaction of allyl halides 1 with alkynyltins 3 in the presence of "Ni(PR3)n" (R = Ph, OEt, or OPh) catalyst was carried out in THF at reflux to give 1,4-enynes.The regioselectivity of the coupling of 1f-i with 3a was investigated in the presence of various phosphorus ligands.Interestingly, prenyl (1j) and geranyl chlorides (1k) selectively reacted with 3 at the more-hindered positions of substituted η³-allylnickel intermediates 21 (M = Ni) to yield 23 and 25, respectively.Regioselectivity in these reactions may result from greater steric crowding between the phosphorus ligand and the disubstituted position in 26b than in 26a.In contrast, the palladium-catalyzed reactions of 1j and 1k with 3 selectively gave 22 and 24, respectively.Thus, the steric crowding in a Pd analogue of 26b is less than that in a Ni analogue of 26b, since Pd has a larger covalent radius than Ni.