TITANIUM-CATALYZED BIS(TRIMETHYLSILYL)BUTA-1,3-DIYNE(2]CYCLOADDITIONSAND [6+2]CYCLOADDITIONS OF 1,4)

The (C2H5)(2)AlCl/TiCl4 catalyst induces the [4+2] cycloaddition of bu tadiene or the [6+2] cycloaddition of 1,3,5-cycloheptatriene (CHT) to individual acetylenic moieties of 1,4-bis(trimethylsilyl)buta-1,3-diyn e (BSD). Heating of the 2:1 butadiene adduct, bis(2-trimethylsilylcycl ohexa-1,4-dien-1-yl), to 250 degrees C yields 2,2'-bis(trimethylsilyl) biphenyl. The 1:1 adduct of BSD with CHT, imethylsilyl-8-trimethylsily lethynylbicyclo[4.2.1] nona-2,4-diene, is obtained as virtu ally the o nly product if the initial molar ratio CHT:BD equal to 1.86 is used.