Silaheterocyclen. XI. Erzeugung und Cycloadditionsverhalten des Diphenylneopentylsilaethens, Ph2Si=CHCH2tBu

Article abstract of DOI:10.1016/0022-328X(92)83156-C

Diphenylneopentylsilene, Ph2Si=CHCH2^tBu (3), is prepared as a reactive intermediate by the reaction of diphenylvinylchlorosilane (1) with Li^tBu in nonpolar solvents via the α-lithioadduct Ph2Si(Cl)CH(Li)CH2^tBu (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.