Mixed carboxylic–sulfonic anhydride in reaction with imines: a straightforward route to water-soluble β-lactams via a Staudinger-type reaction?

Organic & Biomolecular Chemistry Pub Date: 2018-05-08 DOI: 10.1039/C8OB00768C

Abstract

The first example of employing a mixed carboxylic–sulfonic anhydride in reaction with imines is reported. Unlike its well-studied isostere homophthalic anhydride, benzo[c][1,2]oxathiin-3(4H)-one 1,1-dioxide gave no product of a formal [4 + 2] cycloaddition and only followed an alternative reaction pathway toward β-lactams, presumably, via a formal [2 + 2] cycloaddition (a Staudinger-type reaction). Optimized reaction conditions involve the use of triethylamine as a base promoter, which also allows isolating the product β-lactam benzene sulfonic acids as respective triethylammonium salts by conventional column chromatography. The reaction shows some preference to trans-isomer formation; pure diastereomers can be isolated in some cases.

Graphical abstract: Mixed carboxylic–sulfonic anhydride in reaction with imines: a straightforward route to water-soluble β-lactams via a Staudinger-type reaction
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