Simple Access to 2,5-Disubstituted Thiazoles via Cyclisation of N-Substituted α-Amino Acids

We report a mild, metal-free synthesis of 2,5-disubstituted thiazoles from readily available N-substituted α- amino acids. The reaction proceeds via carboxylic acid activation with thionyl chloride, followed by intramolecular cyclisation and in situ sulfoxide deoxygenation, affording the target thiazoles in excellent yields. This transition-metal-free, robust, and scalable protocol enables access to a broad range of 2,5-disubstituted thiazoles, bypassing the need for complex reagents and significantly simplifying their synthesis.