Stereoselective synthesis of 2-spirocyclopropyl-indolin-3-ones through cyclopropanation of aza-aurones with tosylhydrazones?

Organic & Biomolecular Chemistry Pub Date: 2021-04-06 DOI: 10.1039/D1OB00076D

Abstract

A simple and efficient approach for the synthesis of 2-spirocyclopropyl-indolin-3-ones is herein described. The method involves a diasteroselective cyclopropanation of aza-aurones with tosylhydrazones, selected as versatile carbene sources, and represents a remarkable synthetic alternative to get access to this class of C2-spiropseudoindoxyl scaffolds. The reactions proceed in the presence of a base and catalytic amounts of benzyl triethylammonium chloride and well-tolerate a broad range of substituents on both aza-aurones and tosylhydrazones to afford a series of C2-spirocyclopropanated derivatives in high yields. In addition, selected functional group transformations of the final products were explored demonstrating the synthetic potential of these indole-based derivatives.

Graphical abstract: Stereoselective synthesis of 2-spirocyclopropyl-indolin-3-ones through cyclopropanation of aza-aurones with tosylhydrazones
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