Kazutoshi Ikenaga

Reaction of diazonium salts with transition metals: IX. Reaction of vinyltrimethylsilane with arenediazonium tetrafluoroborates under palladium(0) catalysis☆

Arenediazonium tetrafluoroborates (ArN2BF4 where ArPh, 4-MeC6H4, 4-BrC6H4, 4-IC6H4 and 4-NO2C6H4) reacted easily with CH2CHSiMe3 at 25 δC to give ArCHCH2, (E-ArCHCHSiMe3 and Ar(Me3Si)CCH2 in excellent yields under palladium(O) catalysis. (E)-ArCHCHSiMe3 compounds were obtained predominantly and isolated in good yields by using an excess of CH2CHSiMe3 over ArN2BF4. Protodesilylation of the reaction mixture afforded styrene derivatives.

Stereospecific phenylation of alkenylsilanes with phenylpalladium acetate

Abstract (E)- and (Z)-RCH=CHSiMe 3 (R=Ph, n-C 6 H 13 , CH 3 OCH 2 ) reacted stereospecifically with Ph-Pd-OAc to give RCH=C(Ph)SiMe 3 and R(Ph)C=CHSiMe 3 with inversion of the starting geometry with respect to R and Me 3 Si groups.

Reaction of diazonium salts with transition metals. Part 11. Palladium-catalyzed aryldesilylation of alkenylsilanes by arenediazonium salts

Under palladium(0) catalysis, both (E)- and (Z)-RCHCHSiMe3(RRh, 4-MeC6H4, 4-NO2C6H4, n-C6H13, and MeOCH2) were easily aryldesilylated by ArN2X (ArPh, 4-MeC6H4, 4-BrC6H4 and 4-NO2C6H4; XBF4, PF6, and Cl) to give (E)-RCHCHAr and RC(Ar)CH2 as the main products at 25 °C in acetonitrile. anti- and syn-1,2-Elimination of Pd(0) and Me3Si from the adducts, threo- and erythro-RCH(PdX)CHSiMe3, generated from ArPdX and (E) and (Z)-RCHCHSiMe3, respectively, are proposed for the formation of (E)-RCHCHAr from either isomer of RCHCHSiMe3.

Experimental and theoretical study on thermodynamic stabilities of silyl cations. Substituent effect on the stability of dimethylphenylsilyl cation in the gas phase

Thermodynamic stabilities of aryldimethylsilyl cations were determined by measuring equilibrium constants of hydride-transfer reaction in the gas phase using a FT ion cyclotron resonance spectrometer. An application of the Yukawa–Tsuno equation to the substituent effect gave a ρ of –5.87 and an r+ of 0.29. Both r+ and ρ values are significantly smaller than those for a carbon analog, α-cumyl cation. The same trend was observed for the results of ab initio calculations. In addition, the r+ value of 0.3 for gaseous silyl cations agrees with that observed for the kinetics of the hydride-transfer reaction from aryldimethylsilanes to diarylcarbenium ions in dichloromethane. It is concluded that the dimethylphenylsilyl cation is characterized by no significant π-delocalization of the positive charge into the benzene ring in addition to a small ρ value compared to that of the α-cumyl cation.