I₂‑Catalyzed Oxidative N–S Bond Formation: Metal-Free Regiospecific Synthesis of N‑Fused and 3,4-Disubstituted 5‑Imino-1,2,4-thiadiazoles

A novel and expeditious approach for the synthesis of N-fused and 3,4-disubstituted 5-imino-1,2,4-thiadiazole derivatives has been achieved through the molecular iodine-catalyzed oxidative cyclization of 2-aminopyridine/amidine and isothiocyanate via N–S bond formation at ambient temperature. The present one-pot transition-metal-free protocol provides the facile and highly efficient regiospecific synthesis of various 1,2,4-thiadiazole derivatives in a scaled-up manner with good to excellent yields using inexpensive I2 as a catalyst.本研究已成功开发出一种新颖高效的合成方法，可用于制备氮稠合（N-fused）与3,4-二取代5-亚氨基-1,2,4-噻二唑（1,2,4-thiadiazole）衍生物；该方法以分子碘（molecular iodine）为催化剂，在室温条件下通过2-氨基吡啶/脒与异硫氰酸酯的氧化环合反应构建N-S键，实现目标产物的合成。本研究所采用的无过渡金属一锅法方案，以廉价的I₂为催化剂，能够便捷、高效且区域专一地合成多种1,2,4-噻二唑衍生物，可实现放大规模制备，产物收率可达良好至优异水平。