已开发出丙二酸半硫酯(MAHT)与2-芳基取代的乙烯基砜的不对称脱羧1,4-加成反应,产生的加合物具有出色的对映选择性(最高ee达97%)。考虑到调整p K a值,设计并证明了基于奎宁的苄基取代的硫脲是最有效的催化剂。由脱羧的1,4加成加合物完成了3-甲基茚满酮和(+)-姜黄酮的3-单氟化类似物的对映选择性合成。
Organocatalytic Michael Addition of Aldehydes to Vinyl Sulfones: Enantioselective α-Alkylations of Aldehydes and Their Derivatives
作者:Qiang Zhu、Yixin Lu
DOI:10.1021/ol8019296
日期:2008.11.6
Organocatalyticasymmetric Michael reaction of unmodified aldehydes to vinyl sulfones catalyzed by silylated biarylprolinol afforded the desired Michael products with exceptional enantioselectivity. The described enantioselective addition to vinyl sulfones, in combination with desulfonation, offers a unique, asymmetric entry to alpha-alkylated aldehydes and their derivatives.
Asymmetric Michael Addition of 5 <i>H</i>-Oxazol-4-ones to Vinyl Sulfones: Stereoselective Synthesis of Monofluorinated Analogs of 2-Tertiary Hydroxyl-3-Methyl-Substituted Carboxylic Acidl Derivatives
AbstractAn asymmetric Michael addition of 5H‐oxazol‐4‐ones to vinyl sulfones has been developed. In the presence of 10 mol % of quinine‐based benzyl‐substituted thiourea as catalyst at 0 °C, the products could be obtained with excellent enantio‐ and diastereoselectivity (up to>99 % ee and>20:1 dr). 1.0 mol % of catalyst also produced the corresponding adducts with similar stereoselective results when the temperature was increased to 25 °C. The obtained adducts have been demonstrated as significant synthetic fragments to conveniently access the monofluorinated analogs of biologically important 2‐tertiary hydroxyl‐3‐methyl‐substituted carboxylic acid derivatives.magnified image