We have established that a cationic rhodium(I)-H8-BINAP complex catalyzes the complete intermol. homo-[2+2+2] cycloaddn. of aryl ethynyl ethers and cross-[2+2+2] cycloaddn. of aryl ethynyl ethers with electron-deficient monoalkynes, leading to tri- and diaryloxybenzenes, resp., at room temp. [on SciFinder(R)]