Regiodivergent Synthesis of 1,3-and 1,4-Enynes through Kinetically Favored Hydropalladation and Ligand-Enforced Carbopalladation

摘要

Pd-catalyzed hydroalkynylations were developed that involve ligand-enabled regiodivergent addition of an alkyne to an allenamide, giving branched and linear products stereoselectively and facilitated by the neighboring amide group. Regioselectivity was achieved with the use of (o-OMePh)(3)P and BrettPhos, which allowed the functionalization of various alkynes, including steroids, carbohydrates, alkaloids, chiral ligands, and vitamins. Based on the experimental results, it was proposed that hydro- and carbopalladation processes operated during the formations of the branched and linear products, respectively.