Ph ₂ SCCO: A New Versatile CCO‐Fragment Transfer Reagent

Abstract

Abstract ketenylidene (C 2 O) is an electronically intriguing small molecule with significant potential as a C 2 synthon in organic synthesis. However, its high reactivity has thus far precluded practical applications. Herein, we report the synthesis of a new reagent, the heterocumulene Ph 2 S═C═C═O ( 1 ), a well‐defined C 2 O equivalent that accurately replicates the chemical reactivity profile of C 2 O in a controlled manner. 1 uniquely integrates ketene‐like and classical carbene reactivity. In the presence of Brønsted acids, 1 undergoes initial 1,2‐addition to form a sulfur ylide intermediate, which can be exploited for subsequent reactions including cyclopropanation, epoxidation, or X–H addition. The CCO fragment transfer strategy, starting from simple precursors, enables efficient access to α‐cyclopropyl‐ as well as α‐epoxy‐carbonyl derivatives and structurally complex bicyclic cyclopropanes.