Ortho-Nitro Effect on the Diastereoselective Control in Sulfa-Staudinger and Staudinger Cycloadditions
Zhanhui Yang1, Hassane Abdellaoui2, Wei He3
1State Key Laboratory of Chemical Resource Engineering, Department of Organic Chemistry, Faculty of Science, Beijing University of Chemical Technology, Beijing 100029, China. zhyang_2008a@163.com.
Abstract:
The ortho-nitro effect was discovered in sulfa-Staudinger cycloadditions of ethoxycarbonylsulfene with linear imines. When an ortho-nitro group is present at the C-aryl substituents of linear imines, the sulfa-Staudinger cycloadditions deliver cis-β-sultams in considerable amounts, together with the predominant trans-β-sultams. In other cases, the above sulfa-Staudinger cycloadditions give rise to trans-β-sultams exclusively. Further mechanistic rationalization discloses that the ortho-nitro effect is attributed to its strong electron-withdrawing inductive effect. Similarly, the ortho-nitro effect also exists in Staudinger cycloadditions of ethoxycarbonyl ketene with the imines. The current research provides further insights into the diastereoselective control in sulfa-Staudinger and Staudinger cycloadditions.
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