|Budget Amount *help
¥6,400,000 (Direct Cost : ¥6,400,000)
Fiscal Year 1990 : ¥900,000 (Direct Cost : ¥900,000)
Fiscal Year 1989 : ¥5,500,000 (Direct Cost : ¥5,500,000)
Kinetics and products have been investigated in detail for the solvolysis of alpha- or beta-silyl-substituted benzylic derivatives, i. e., alpha- (pentamethyldisilanyl) benzyl halides (1), 2, 2, 3, 3-tetramethy1-2, 3-disila-1-indanyl chloride (2), 2, 2-dimethy1-2-sila-1-indanyl halides (3), 1-pheny1-2-(trimethylsily) ethyl trifluroacetate (4), 2-phenyl-1- (pentamethyldisilanyl) cyclopropyl bromide (5), and 2-phenyl-2- (trimethylsilyl) ethyl trifluroacetate (6), and other related derivatives. The following observations are instructive. (1) alpha-Silicon destabilizes the benzylic cation by 3-4 kacal/mol relative to carbon ; (2) alpha- (Disilanyl) benzyl cation and alpha- (trimethylsilylmethyl) -benzyl cation are respectively 6.2-6.8 and 7.2 kcal/mol more stable than the corresponding alpha- (trialkylsilyl) benzyl cation and alpha-alkylbenzyl cation ; (3) 1 solvolyzes via kc mechanism despite a marked rate acceleration by the beta-silyl group and a rearrangement of this group seemingly characteristic of sigma-participation ; (4) The alpha-disilanyl compound 2 in which the Si-Si bond is orthogonal to the leaving group exhibits no beta-silicon effect indicative of hyperconjugative origin for the betasillic on effect ; (5) In sigma-participated (4) or aryl-paticipated solvolysis (5), the presence of the beta-silicon allows the kc solvolysis to occur exclusively or competitively.