Umpolung of the reactivity of allylsilanes. Palladium(II) catalyzed cyclization of allylsilyl alcohols: a new route to substituted 2-vinyltetrahydrofurans
摘要:
Functionalized allylsilanes 1-4 undergo palladium(II) catalyzed ring closure to afford 4- and/or 5-substituted 2-vinyltetrahydrofurans (5-8) under mild conditions. The catalytic reactions proceed through (eta(3)-allyl)palladium intermediates formed by palladadesilylation of the allylsilane substrates. (C) 2000 Elsevier Science Ltd. All rights reserved.
Synthesis of stereodefined vinyl-tetrahydropyran and vinyl-octahydrochromene derivatives via acetalization–cyclization of allylsilanes with aldehydes. Origin of the high stereoselectivity
作者:Johan Kjellgren、Kálmán J. Szabó
DOI:10.1016/s0040-4039(01)02340-1
日期:2002.2
Functionalized allylsilanes 1-5 and aldehydes 6-8 undergo Lewis-acid mediated ring closure to afford 2,3,5- or 6-substituted tetrahydropyrans (8 15) and 2,3-substituted octahydrochromenes (16a-b) with excellent stereoselectivity. According to DFT calculations the high stereoselectivity arises from electronically induced steric effects occurring in the key-intermediate of the cyclization. (C) 2002 Elsevier Science Ltd. All rights reserved.