Benzyne‐Promoted Curtius‐Type Rearrangement of Acyl Hydrazides in the Presence of Nucleophiles

Abstract A protocol has been developed for the Curtius‐type rearrangement of acyl hydrazides in the presence of nucleophiles by activating acyl hydrazides with benzyne to generate aminimide intermediates. A wide variety of N′ ‐methyl‐ N ′‐phenyl acyl hydrazides were treated with various alcohols in the presence of 2‐(trimethylsilyl)phenyl triflate and CsF under mild conditions to afford structurally diverse carbamates in moderate to excellent yields. Importantly, complete retention of configuration was observed in the reaction of enantioenriched α‐chiral alkanoyl hydrazides. Replacing the alcohol with water, an amine, an N′ ‐unsubstituted acyl hydrazide, an alkoxyamine, or a thiophenol in the reaction permitted facile synthesis of ureas and analogues.