Alkoxyallylsilanes: Functional protecting groups

Allyl-t-butylmethylsilyl groups were shown to function as alcohol protectin g groups whose hydrolytic stability was greater than t-butyldimethylsilyl ( TBS) and Si(SiMe3)(3) (sisyl) groups. Pseudo-first-order rate constants for the acidic hydrolysis of primary, benzylic, and secondary allyl-t-butylmet hylsilyl ethers in AcOD/THF-d(8)/D2O were determined to be 2.94x10(-3), 8.2 6x10(-4), and 8.26x10(-4)s(-1) respectively. The regioselectivity of acidic hydrolysis of allylbenzyloxy-t-butylmethylsilane 1 was examined under stro ng acid (p-TsOH/ CD2Cl2) and weak acid (AcOD/HF-d(8)/D2O) conditions. In bo th cases, benzyl alcohol was initially produced exclusively from silicon-ox ygen bond cleavage: allylic cleavage was only subsequently observed over ti me. However, the allyl group of the silyl ether could be hydrosilylated. Th e resulting alkoxy-functionalized disiloxane had greater hydrolytic stabili ty under acidic conditions than the starting alkoxyallyl-t-butylmethylsilan e. (C) 2000 Elsevier Science Ltd. All rights reserved.