Steric-Hindrance-Induced Diastereoselective Radical Nitration of 3-Alkylidene-2-oxindoles Followed by Tosylhydrazine-Mediated Sulfonation
作者:Sayan Pramanik、Pinaki Saha、Prasanta Ghosh、Chhanda Mukhopadhyay
DOI:10.1021/acs.joc.2c01523
日期:2023.3.17
Metal-free radical nitration of the β C–H bond of 3-alkylidene-2-oxindoles with tert-butyl nitrite (TBN) has been explored. Interestingly, (E)-3-(2-(aryl)-2-oxoethylidene)oxindole and (E)-3-ylidene oxindole give different diastereomers on nitration. The mechanistic investigation revealed that the diastereoselectivity was controlled by the size of the functional group. Another transformation of 3-(nitroalkylidene)
已经探索了 3-alkylidene-2-oxindoles 的 β C-H 键与亚硝酸叔丁酯 (TBN)的金属自由基硝化反应。有趣的是,( E )-3-(2-(aryl)-2-oxoethylidene)oxindole 和 ( E )-3-ylidene oxindole 在硝化时给出不同的非对映异构体。机理研究表明,非对映选择性受官能团大小的控制。通过金属和无氧化剂的甲苯磺酰肼介导的磺化作用,将 3-(硝基亚烷基) 羟吲哚转化为 3-(甲苯磺酰亚烷基) 羟吲哚。这两种方法都具有起始材料容易获得和操作简单的优点。