Regioselective Cleavage and Reconfiguration of C-S Bonds with Diazo Compounds.

A coupling reaction between diazo compounds and phenyl benzyl sulfide catalyzed by TfOH has been reported. This reaction can synthesize important α-arylthio carbonyl compounds via regioselective cleavage and reconfiguration of C-S bonds, and various functional groups were tolerant to the reaction conditions. Mechanistic studies have conclusively established that the pivotal intermediate in the reaction was meticulously investigated through spectroscopic evidence, complemented by rigorous control experiments.

Synthesis of 2,4-Disubstituted Oxazoles and Thiazoles via Brønsted Acid-Catalyzed Cyclization of α-diazoketones with Amides.

A novel method is described for the synthesis of 2,4-disubstituted oxazole and thiazole derivates via the coupling of α-diazoketones with (thio)amides or thioureas using trifluoromethanesulfonic acid (TfOH) as a catalyst. This protocol is characterized by mild reaction conditions, metal-free, and simplicity and also features good functional group tolerance, good to excellent yields, and a broad substrate scope with more than 40 examples. Experimental studies suggest a mechanism involving 2-oxo-2-phenylethyl trifluoromethanesulfonate as the key intermediate.