Fluoroboric acid adsorbed on silica-gel (HBF4–SiO2) as a new, highly efficient and reusable heterogeneous catalyst for thia-Michael addition to α,β-unsaturated carbonyl compounds
作者:Gaurav Sharma、Raj Kumar、Asit K. Chakraborti
DOI:10.1016/j.tetlet.2008.04.144
日期:2008.6
found to be a new and highly efficient heterogeneouscatalyst for thia-Michael addition to α,β-unsaturated carbonyl compounds under solvent-free conditions. In the case of 1,3-diaryl-2-propenones, the reactions are best carried out in MeOH. The rate of thia-Michael addition was dependent on the steric hindrance at the β-carbon of the α,β-unsaturated carbonyl substrate as well as surrounding the thiol
Scope and limitations of HClO4–SiO2 as an extremely efficient, inexpensive, and reusable catalyst for chemoselective carbon–sulfur bond formation
作者:Gopal L. Khatik、Gaurav Sharma、Raj Kumar、Asit K. Chakraborti
DOI:10.1016/j.tet.2006.11.050
日期:2007.1
cyclic and acyclic α,β-unsaturatedketones afforded excellent yields of the corresponding β-sulfidocarbonyls after 2 min to 2 h. In the case of dithiols, the bis-thia-Michael adducts were formed. The rate of the reaction was found to be dependent on the electronic and steric factors of the α,β-unsaturatedketones and the thiols. A substituent at the β-carbon of the α,β-unsaturatedketone offered steric
The highly enantioselective organocatalytic sulfa-Michael addition to α,β-unsaturatedketones has been accomplished using benzyl and tert-butyl mercaptans as the sulfur-centered nucleophiles. Optically active products are obtained in high yields and good to excellent stereocontrol (up to 96 % ee) from a large variety of enones. Central to these studies has been the use of the catalytic primary amine
使用苄基和叔丁基硫醇作为以硫为中心的亲核试剂,已经完成了对α,β-不饱和酮的高对映选择性有机催化磺胺-迈克尔加成反应。从多种烯酮中以高收率和良好至优异的立体控制(高达96%ee)获得光学活性产品。这些研究的核心是衍生自9-氨基-(9-脱氧)-表氢对苯二酚和D - N - Boc-苯基甘氨酸的催化伯胺盐A的使用,其中阳离子和阴离子均为手性,对烯酮的亚胺离子催化具有高反应活性和选择性。