One-pot synthesis of unsymmetrical disulfides using 1-chlorobenzotriazole as oxidant: Interception of the sulfenyl chloride intermediate

A high-yielding and low temperature one-pot procedure is described for unsymmetrical disulfide synthesis from two different thiols using 1-chlorobenzotriazole (BtCl) as oxidant. The mechanism of the coupling involves in situ trapping of the sulfenyl chloride intermediate R(1)SCl by nucleophilic benzotriazole (BtH) to form R(1)SBt, which protects R(1)SCl from forming the homodimer R(1)SSR(1). The methodology is applicable to all types of thiol (aliphatic, aromatic, heteroaromatic), with a variation developed for aliphatic-aliphatic couplings. Differentially N-protected cysteines couple to afford the unsymmetrical cystine derivatives in high yield (90%), which serves as a model for the one-pot intermolecular coupling of cysteine-containing peptides to form peptide disulfide heterodimers. Minimal exchange in aromatic-aromatic disulfide synthesis is noted on account of the mild conditions. (C) 2010 Elsevier Ltd. All rights reserved.