Regiocontrol in the palladium-catalyzed hydrophosphinylation of terminal alkynes

The regioselectivity of the palladium-catalyzed hydrophosphinylation of terminal alkynes was investigated. Complementary conditions to achieve the predominant formation of either the linear or the branched alkenyl-H-phosphinate products were identified. With Pd/xantphos in acetonitrile, the linear isomer is generally obtained with good to excellent selectivity, and E-stereospecificity. On the other hand, by using Pd/dppf in the non-polar solvent toluene, good selectivity for the branched alkenyl-H-phosphinate is typically observed. The role of various reaction parameters is studied.