THE ACID-INDUCED REARRANGEMENT OF 1-HYDROXYALKYLTRIS(TRIMETHYLSILYL)SILANES

In the presence of strong acids, such as HCl or H2SO4, 1-hydroxyalkylt ris(trimethylsilyl) silanes (Me3Si)(3)Si-C(OH)(RR2)-R-1 (1a-f) isomeri ze by 1,2-Me3Si/OH exchange to give the trimethylsilylmethylsilanols ( Me3Si)(2)Si(OH)-C(SiMe3)(RR2)-R-1 (4a-f) [R-1,R-2: a: Me, Me; b: H, 4- MeC6H4; c: H, 4-iPrC(6)H(4); d: H, Mes; e: H, 2-Me2NC6H4; f: H, 2,4,6- (MeO)(3)C6H2]. A mechanism for the isomerization is proposed. In the c ase of the reaction of Id with sulfuric acid, the silylsulfate (Me3Si) (2)-Si(OSO3H)-C(SiMe3)HMes (5) was isolated. 5 is the intermediate in the H2SO4-catalyzed isomerization of Id and was converted in situ with methanol, acetic anhydride, HF or HCl to give the respective methoxys ilane 6, acetoxysilane 7, fluorosilane 8, or chlorosilane 9. Deprotona tion of 4a, d, f with sodium hydride causes a further rearrangement, a 1,3-C,O-trimethylsilyl migration, to give the siloxanes (Me3Si)(2)(Me 3-SiO)Si-(CHRR2)-R-1 (11a, d, f).