[3,3]-Sigmatropic rearrangement of silyl ketene acetals of methyl α-(allyloxy) acetates.
作者:Stanley Raucher、Linda M Gustavson
DOI:10.1016/s0040-4039(00)84311-7
日期:1986.1
Although the lithium enolate undergoes [2,3]-sigmatropic rearrangement to give , the silylketeneacetals undergo [3,3]-sigmatropic rearrangement to give . This is the first reported [3,3]-sigmatropic rearrangement of a 1,1-dioxy-3-oxa-1,5-diene.
The lithium ester and ketone enolates (generated in HMPA-THF) and the dilithiated oxime (generated in THF) are shown to serve well as the migrating terminus for the [2,3]Wittig shift, not for the [3,3]Claisen shift. On the basis of these observations, the solution structures of the “lithium enolates” are discussed.
A novel silyl triflate-mediated [2,3]sigmatropicrearrangement of (allyloxy)acetates and their ketene silyl acetals is described, which is proposed to proceed via rarely precedented oxygen ylides. The formal [2,3]Wittlg shift is characterized by the unique stereoselectivity, , the rarely precedented -selectivity and the high erythro-selectivity.
Aerobic Oxidative Cyclization under Pd(II) Catalysis: A Regioselective Approach to Heterocycles
作者:Kai-Tai Yip、Jin-Heng Li、On-Yi Lee、Dan Yang
DOI:10.1021/ol052529c
日期:2005.12.1
An efficient Yb(OTf)(3)-promoted palladium-catalyzed oxidative cyclization of gamma-heteroalkenyl beta-keto amides has been developed. Under simple aerobic condition, a variety of six-, seven-, and eight-membered-ring N- and O-heterocycles were obtained regioselectively in excellent yield.
RAUCHER, S.;GUSTAVSON, L. M., TETRAHEDRON LETT., 1986, 27, N 14, 1557-1560