SILAHETEROCYCLES .11. PRODUCTION AND CYCLOADDITION BEHAVIOR OF DIPHENYLNEOPENTYLSILAETHENE, PH2SI=CHCH2TERT-BU

Diphenylneopentylsilene, Ph2Si = CHCH2tBu (3), is prepared as a reactive intermediate by the reaction of diphenylvinylchlorosilane (1) with Li(t)Bu in nonpolar solvents via the alpha-lithioadduct Ph2Si(Cl)CH(Li)CH2tBu (2). This lithiated species can be trapped by trimethylsilyltriflate and yields silene 3 by 1,2-LiCl-elimination. Without suitable Si = C-trapping agents, the E/Z-isomeric tetraphenyl-2,4-dineopentyl-1,3-disilacyclobutane (6) is formed by cyclodimerization. In the presence of dienes like 2,3-dimethyl (DMB)- and 2-methyl-1,3-butadiene (MBD) the Diels-Alder and ene-products are formed in competition, while the cycloaddition of 3 with norbornadiene, cyclohexa-1,3-diene, cyclopentadiene and anthracene yields the [2 + 2 + 2]- or the [4 + 2] products exclusively. Exo/endo-{2,2-diphenyl-3-(2',2'-dimethylpropyl)-2-silabicyclo[2.2.2]oct-5-ene} (19) is a crystalline solid as well as compound E-6, whose structures are presented in this paper.