Diastereoselective anodic hetero- and homo-coupling of menthol-, 8-methylmenthol- and 8-phenylmenthol-2-alkylmalonates
作者:Matthias C Letzel、Hans J Schäfer、Roland Fröhlich
DOI:10.3762/bjoc.13.5
日期:——
Diastereoselective radical coupling was achieved with chiral auxiliaries. The radicals were generated by anodic decarboxylation of five malonic acid derivatives. These were prepared from benzyl malonates and four menthol auxiliaries. Coelectrolyses with 3,3-dimethylbutanoic acid in methanol at platinum electrodes in an undivided cell afforded hetero-coupling products in 22-69% yield with a diastereoselectivity
非对映选择性自由基偶联是通过手性助剂实现的。这些自由基是通过五种丙二酸衍生物的阳极脱羧反应生成的。它们是由丙二酸苄酯和四种薄荷醇助剂制备的。在未分开的电池中,在铂电极上与甲醇中的3,3-二甲基丁酸进行共电解,可得到杂耦合产物,产率为22-69%,非对映选择性为5至65%de。没有助酸的电解质以21-50%的产率产生非对映异构体均偶联产物,非对映异构体的比率为1.17:2.00:0.81至7.03:2.00。X射线结构分析和13 C NMR数据证实了新的立体异构中心的立体化学。