Theoretical Study of the Copper-Catalyzed Hydroarylation of (Trifluoromethyl)alkyne with Phenylboronic Acid

Abstract

The copper-catalyzed hydroarylation of 1,1,1-trifluoro-2-butyne with phenylboronic acid was investigated by performing density functional theory calculations, and a plausible mechanism was proposed. The initial transmetalation step was first examined to compare the feasibility of the catalytically active copper species. Subsequently, the carbocupration of 1,1,1-trifluoro-2-butyne by the phenylcopper species was examined in terms of regioselectivity. The impacts of the alkyne terminal group and the para-substituents of phenylboronic acids on the carbocupration were also examined. Moreover, to shed light on the role of the electron-withdrawing groups on the alkyne substrates, the activation barrier for the carbocupration of 1,1,1-trifluoro-2-butyne was compared to those for several alkyne substrates bearing ester, ketone, cyano, and pentafluorophenyl groups, as well as 2-butyne, which has no electron-withdrawing group. The final protodecupration step involving methanol, acetic acid, or phenylboronic acid was examined to determine possible proton donors.