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-unsaturated ketones 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-unsaturated ketones and the thiols. A substituent at the β-carbon of the α,β-unsaturated ketone offered steric
高氯酸吸附在硅胶上的范围和限制(HClO 4 -SiO 2)是一种高效,廉价且可重复使用的催化剂,可通过在无溶剂条件下和室温下将硫醇共轭添加到α,β-不饱和酮上来形成化学选择性碳-硫键。对于1,3-二苯基丙烯酮,反应最好在无溶剂条件下于80°C或在室温下于MeOH中进行。芳基,芳基烷基,烷基硫醇和烷烃二硫醇与环状和无环α,β-不饱和酮反应后,在2分钟至2小时后,其相应的β-硫代羰基羰基化合物的收率极高。在二硫醇的情况下,形成了二硫杂-迈克尔加合物。发现反应速率取决于α,β-不饱和酮和硫醇的电子和空间因素。α的β-碳原子上的取代基,β-不饱和酮为共轭物的添加提供了空间位阻,此类底物需要更长的时间。在芳族硫醇的情况下,硝基的存在降低了巯基硫原子的亲核性,导致4-硝基硫代苯酚的反应速率低于硫代苯酚和4-甲基硫代苯酚的反应速率。对于烷硫醇,反应速率受连接至巯基部分的烷基的空间拥挤影响。与芳基硫醇相