A cationic rhodium(I)/(R)-H8-BINAP or (R)-Segphos complex catalyzes an intramol. [2 + 2 + 2] cycloaddn. of unsym. dienynes, leading to fused tri- and tetracyclic cyclohexenes bearing two tertiary or quaternary carbon centers in high yields with high enantio- and diastereoselectivity. [on SciFinder(R)]