In Situ Formation of Vilsmeier Reagents Mediated by Oxalyl Chloride: a Tool for the Selective Synthesis of <i>N</i>‐Sulfonylformamidines

Abstract

Abstract N ‐Sulfonylformamidines were produced from sulfonamides or N ‐acylated sulfonamides using Vilsmeier reagent obtained in situ from N , N ‐disubstituted formamides and oxalyl chloride. Optically active substrates did not racemize during the process. The efficient and mild cleavage of N ‐sulfonylformamidines can be achieved with hydrazine hydrate in ethanol. The entire procedure constitutes a simple method for protecting, and deprotecting, the sulfonamide moiety.