Catalyst-Free Conjugated Addition of Thiols to α,β-Unsaturated Carbonyl Compounds in Water
作者:Gopal L. Khatik、Raj Kumar、Asit K. Chakraborti
DOI:10.1021/ol060846t
日期:2006.5.1
[reaction: see text] Catalyst-free conjugateaddition of thiols to alpha,beta-unsaturated carbonylcompounds in water is reported. beta-Sulfido carbonylcompounds were formed at room temperature, in short times and with excellent chemoselectivity. Competitive dithiane/dithiolane formation, transesterification, and ester cleavage were not observed. Water played a dual role in simultaneously activating
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
Copper(II) tetrafluoroborate as a novel and highly efficient catalyst for Michael addition of mercaptans to α,β-unsaturated carbonyl compounds
作者:Sanjeev K. Garg、Raj Kumar、Asit K. Chakraborti
DOI:10.1016/j.tetlet.2005.01.051
日期:2005.3
been found to be a new and highlyefficient catalyst for Michaeladdition of thiols to α,β-unsaturated carbonyl compounds under solvent-free conditions and in H2O at room temperature. The reactions are very fast and are completed in 2 min to 1 h affording high yields. The rate of thiol addition was dependent on the steric hindrance at the β-carbon of the α,β-unsaturated carbonyl substrate. In the case
Zinc Perchlorate Hexahydrate Catalysed Conjugate Addition of Thiols to α,β-Unsaturated Ketones
作者:Asit K. Chakraborti、Sanjeev K. Garg、Raj Kumar
DOI:10.1055/s-2005-868480
日期:——
provides a means to carry out the reaction under versatile experimental conditions. The rate of thiol addition was dependent on the electronic and steric factors of the enones and the thiols. The substituent at the β-carbon of the α,β-unsaturated ketone substrate caused steric hindrance during conjugateaddition and required longer reaction times. The rate of reaction for alkane thiols e.g. ethanethiol was
已发现六水合高氯酸锌 (II) 是一种新型高效催化剂,可在室温下无溶剂条件下将硫醇与 α,β-不饱和酮共轭加成。芳基、芳烷基和烷基硫醇与环状和非环状 α,β-不饱和酮的反应在 5 分钟到 6 小时后发生,产率极好。Zn(ClO 4 ) 2 .6H 2 O 与不同溶剂的相容性提供了一种在多种实验条件下进行反应的方法。硫醇加成速率取决于烯酮和硫醇的电子和空间因素。α,β-不饱和酮底物的β-碳上的取代基在共轭加成过程中引起空间位阻,需要更长的反应时间。烷烃硫醇的反应速率,例如