Convenient as well as convergent synthesis of functionalized tetrahydronaphthalenes has been accomplished under mild reaction conditions by the cationic rhodium(I)/H8-BINAP complex-catalyzed [2+2+2] cycloaddn. of 1,7-octadiyne derivs. with functionalized monoynes. The effect of the diyne tether lengths was investigated, which revealed that 1,6-heptadiyne and 1,7-octadiyne exhibit higher reactivity than 1,8-nonadiyne. Mechanistic studies indicated that the present rhodium-catalyzed [2+2+2] cycloaddn. proceeds through the rhodacyclopentadiene intermediate generated by oxidative coupling of a diyne with rhodium. On the other hand, in the reactions of diynes and di-Me acetylenedicarboxylate, the rhodacyclopentadiene intermediate generated by oxidative coupling of a diyne and a monoyne with rhodium would also be involved. [on SciFinder(R)]