Improved <i>E</i>-Selectivity in the Wittig Reaction of Stabilized Ylides with α-Alkoxyaldehydes and Sugar Lactols
作者:Christian Harcken、Stephen F. Martin
DOI:10.1021/ol016729+
日期:2001.11.1
[GRAPHICS]The Wittig reactions of alpha -alkoxyaldehydes and sugar lactols with stabilized ylides such as (alkoxycarbonylmethylene)triphenylphosphoranes typically proceed with low E-selectivities. However, we have discovered that the reaction of such aldehydes with (methoxycarbonylmethylene)tributylphosphorane in toluene in the presence of catalytic amounts of benzoic acid proceeds to give the E-alpha,beta -unsaturated esters with high selectivities and in high yields.
The knoevenagel-doebner reaction on 2,3-O-isopropylidene derivatives of d-ribo and d-manno-furanose
作者:F.Jorge Lopez Herrera、M.Soledad Pino Gonzalez
DOI:10.1016/s0008-6215(00)90309-4
日期:1986.9
Synthesis of enantiomerically pure hydroxylated pyrroline N-oxides from d-ribose
作者:Nikolaos G. Argyropoulos、Theodoros D. Panagiotidis、John K. Gallos
DOI:10.1016/j.tetasy.2006.02.006
日期:2006.3
A convenient way to obtain enantiomerically pure hydroxylated pyrroline N-oxides is reported. The key step is the formation of omega-oxo criciates from (D)-ribose and a subsequent 1,3-azaprotio cyclotransfer reaction of the resulting oximino alkenoate derivatives. The stereochemistry of the nitrones obtained is discussed in relation to that of the starting compounds. (c) 2006 Elsevier Ltd. All rights reserved.