Nickel-catalyzed arylative cyclization of 1,6-enynes: arylation of unactivated alkene moieties

Abstract

We developed a new type of catalytic arylative cyclization of 1,6-enynes, whereby an aryl group is introduced at an unactivated alkene moiety rather than at an alkyne moiety. The reaction of a 1,6-enyne with an arylboronic acid in the presence of an Ni(cod)₂/P(4-MeOC₆H₄)₃ complex yields a five-membered ring product incorporating an all-carbon quaternary center. Experimental studies and extensive DFT calculations reveal that an Ni(I) species is involved in the catalytic cycle, which is an uncommon pathway involving transmetalation, cycloisomerization, selective sp3–sp2 carbon–carbon bond formation, and finally hydrolysis.