RhCl3/amine-catalyzed [2+2+2] cyclization of alkynes

The RhCl3·3H2O/i-Pr2NEt-catalyzed [2+2+2] cyclotrimerization of alkynes has been achieved. The reaction can be widely used for various alkynes and provides tri- or hexa-substituted benzenes regioselectively in high yields. The [2+2+2] cycloaddition of diynes and alkynes is also developed, and it affords benzene derivatives in moderate to high yields.