Catalytic ring-opening allylation of cyclic acetals with allylsilanes using silica-alumina
作者:Ken Motokura、Hirokazu Yoneda、Akimitsu Miyaji、Toshihide Baba
DOI:10.1039/c005033d
日期:——
Ring-opening allylation of cyclic acetals has required stoichiometric amounts of Lewis acids. In this paper, catalytic ring-opening allylation in the presence of silica-alumina is reported. This ring-opening allylation showed high atom economy. Consecutive allylation/hydrolysis using silica-alumina afforded homoallyloxyalcohols in good to high yields.
Stereoselectivity of intramolecular cyclisations of nitrones derived from 3-oxahept-6-enals
作者:Michael B. Gravestock、David W. Knight、Jennifer S. Lovell、Steven R. Thornton
DOI:10.1039/a905802h
日期:——
Intramolecular [1,3]-dipolar cycloadditions of nitrones 33, derived from 3-oxahept-6-enals 7, substituted at either the 4- or 5-position and prepared using a variety of approaches, give good to excellent yields of the cycloadducts 34–37, with good levels of stereoselectivity, especially when the substituent is adjacent to the alkene. The cyclisations appear to proceed via well-defined transition state conformations which should be of predictive value.