A new oxapalladacycle generated via ortho C-H activation of phenylphosphinic acid: an efficient catalyst for Markovnikov-type additions of E-H bonds to alkynes.

A new oxapalladacycle 3 can be conveniently prepared via direct ortho palladation of diphenylphosphinic acid with palladium acetate. Catalysts derived from 3 can efficiently catalyze Markovnikov-type additions of E-H bonds (P(O)-H, S-H and spC-H) to alkynes via a unique catalytic cycle.