TITANIUM-CATALYZED CYCLOADDITION REACTIONS OF PHENYL(TRIMETHYLSILYL)ACETYLENE TO CONJUGATED DIENES AND 1,3,5-CYCLOHEPTATRIENE - 1-PHENYL-2-(TRIMETHYLSILYL)-CYCLOHEXA-1,4-DIENES AND THEIR AROMATIZATION

The catalytic system Et2AlCl/TiCl4 induces Diels-Alder addition of phenyl(trimethylsilyl)acetylene (PTMSA) to 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-methyl-1,3-pentadiene, and [6 + 2] addition of PTMSA to 1,3,5-cycloheptatriene. The 1-phenyl-2-(trimethylsilyl)-cyclohexa-1,4-dienes obtained undergo thermolysis, yielding the corresponding ortho-(trimethylsilyl)biphenyl derivatives. The cyclohexadienes containing vicinal methyl and trimethylsilyl groups evolve methane at 300-degrees-C (the 3-methyl group is released). All other derivatives release hydrogen at only 260-degrees-C.