Nickel Phosphite-Catalyzed Tetradehydro-Diels-Alder Reactions of ( E )-3-ene-1,8-diynes.

A nickel-catalyzed tetradehydro-Diels-Alder reaction of ()-3-ene-1,8-diynes for the preparation of isoindolines, dihydroisobenzofurans, and tetrahydroisoquinolines has been developed. A series of air-stable nickel catalysts were used in this study, including the novel nickel(0)-phosphite catalysts, Ni[P(O-3,5-Me-Ph)], Ni[P(O-1-naphthyl)], and Ni[P(O-2-naphthyl)]. To help understand the type of intermediate in the initial cycloisomerization process, the trapping of nickellacycle intermediates with pinacolborane to yield vinyl boronates is also discussed.