Silicon Effects. VI. β-Silicon Effect of Various Silyl Groups in Solvolysis for α-Alkylbenzyl and α-Silylbenzyl Systems

Article abstract of DOI:10.1246/bcsj.67.500

The kinetic β-silicon effects of various silyl groups including Me3Si, Me3SiMe2Si, (C6H5)Me2Si, (i-PrO)Me2Si, and (CH3OCH2)Me2Si were measured in k_c solvolysis of two different benzylic systems of the types, ArCH(OCOCF3)CH2R (3: Ar=phenyl or 3,5-dichlorophenyl, R=silyl group) and C6H5CH(Cl)SiMe2R (4: R=silyl group).The relative β-silyl accelerations were 1.0:5.57:0.309 for R=Me3Si; Me3SiMe2Si, and (C6H5)Me2Si, respectively, for the system 3, and 1.0:7.65:0.502:0.289 for R=Me3Si, Me3SiMe2Si, (i-PrO)Me2Si, and (CH3OCH2)Me2Si, respectively, for the system 4.The variation of the β-silicon effect with γ-substituents was interpreted as reflecting changes in hyperconjugating abilities of β-C-Si and β-Si-Si ?-bonds mainly due to the inductive effect of the γ-substituent groups.