An asymmetric decarboxylative 1,4‐addition of malonic acid half thioesters (MAHTs) to 2‐aryl‐substituted vinyl sulfones has been developed, yielding adducts with excellent enantioselectivity (up to 97 % ee). In view of tuning pKa values, a quinine‐based benzyl‐substituted thiourea was designed and demonstrated as the most efficient catalyst. The enantioselectivesynthesis of 3‐monofluorinated analogues
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。
<scp>l</scp>-Amino Acid Based Urea–Tertiary Amine-Catalyzed Chemoselective and Asymmetric Stereoablative Carboxylation of 3-Bromooxindoles with Malonic Acid Half Thioesters
An L-amino acid based urea tertiary amine-catalyzed enantioselective stereoablative carboxylation of 3-bromooxindoles with malonic acid half thioesters (MAHTs) and diverse commercially available carboxylic acids has been developed. A series of valuable 3-substituted 3-hydroxy-2-oxindoles were obtained in high enantioselectivities (up to 93% ee). This chemoselective reaction represents the first example of MAHTs as carboxylating agents.