Employment of Palladium Pincer-Complexes in Phenylselenylation of Organohalides

Reaction: see text. Palladium pincer-complex-catalyzed selenylation of propargyl-, allyl-, benzyl-, and benzoyl halides could be achieved under mild reaction conditions employing trimethylstannylphenylselenide as selenylating agent. This reaction has a high functional group tolerance as carbmethoxy, tosylamino, nitro, aryl bromide, and unprotected hydroxy groups are tolerated. Mechanistic studies indicate that the catalytic cycle is initiated by formation of a selenium-coordinated palladium pincer-complex, which subsequently reacts with the electrophilic substrate. DFT calculations were performed to explore the mechanism of the transfer of the organoselenium group from palladium to the substrate. These modeling studies revealed some interesting differences between the mechanism of the organoselenium group transfer and (the previously published) organostannane transfer reactions.