Nickel‐Catalyzed Facile [2+2+2] Cyclotrimerization of Unactivated Internal Alkynes to Polysubstituted Benzenes

A catalytic 2+2+2] cyclotrimerization of unactivated internal alkynes providing cyclotrimerization products in excellent yields with high regioselectivity is described. The transformation is accomplished by using a simple catalytic mixture comprising Ni(acac)₂, an imidazolium salt and a Grignard reagent at room temperature or 60 °C for 20 min or 1 h.