Asymmetric hydrogenation of alkyl(vinyl)thioethers: a promising approach to α-chiral thioethers
摘要:
This paper describes the enantio selective hydrogenation of vinylthioethers. We show that thioether derivatives of maleic esters can be hydrogenated with full conversion and up to 60% ee, and that alpha-thioether cinnamic acids can be hydrogenated in 51% ee with modest conversion. (c) 2007 Elsevier Ltd. All rights reserved.
Thia-Michael Addition Reactions Using 2-[Bis(alkylthio)methylene]-3-oxo-<i>N</i>-<i>o</i>-tolylbutanamides as Odorless and Efficient Thiol Equivalents
作者:Dewen Dong、Qun Liu、Haifeng Yu、Yan Ouyang、Xihe Bi、Yumei Lu
DOI:10.1055/s-2005-923602
日期:——
A series of 2-[bis(alkylthio)methylene]-3-oxo-N-o-tolylbutanamides 1 have been investigated as nonthiolic and odorlessthiolequivalents in thia-Michael addition reactions. The cleavage of compounds 1 is initiated by NaOHin EtOH; the in situ generated thiolate anions undergo facile conjugate addition to α,β-unsaturated carbonyl compounds 2 affording the corresponding β-keto sulfides 3 in very high
Double bonds activated by the electron withdrawing group(s) are cleaved with the reagent system consisting of a hard Lewisacid and ethanethiol to give dithioacetals.
A new protocol for the alkenylation of carbonyl compounds with phosphonates (Horner-Wadsworth-Emmons reaction) is described. Aldehydes react with phosphonates already at room temperature in the presence of triethylamine without further activation by Lewis-acids if high-pressure (8 kbar) is applied to the system. Based on this protocol a domino process was developed combining the HWE reaction with a Michael reaction, thus allowing the one-pot synthesis of β-amino esters, β-thio esters or β-thio nitriles.