The -nitro effect was discovered in sulfa-Staudinger cycloadditions of ethoxycarbonylsulfene with linear imines. When an -nitro group is present at the -aryl substituents of linear imines, the sulfa-Staudinger cycloadditions deliver -β-sultams in considerable amounts, together with the predominant -β-sultams. In other cases, the above sulfa-Staudinger cycloadditions give rise to -β-sultams exclusively. Further mechanistic rationalization discloses that the -nitro effect is attributed to its strong electron-withdrawing inductive effect. Similarly, the -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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| http://dx.doi.org/10.3390/molecules22050784 | DOI Listing |
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