Q-Tube-Assisted Divergent Synthesis of Thiazole and 1,3-Oxathiole Derivatives Using Recyclable Silica-Supported Sodium Carbonate

This study presents an efficient synthetic strategy for heterocycles using silica-supported sodium carbonate as a reusable heterogeneous catalyst under both conventional and Q-Tube high-pressure conditions. The distinct product outcomes observed under conventional reflux and Q-Tube-assisted conditions indicate that the reaction environment influences product selectivity. Because temperature and autogenous pressure vary together in the Q-Tube system, we cannot distinguish their individual contributions in these experiments. Accordingly, the divergent formation of thiazole and 1,3-oxathiole derivatives is attributed to the combined reaction conditions rather than to pressure alone. Green chemistry metrics, including atom economy, reaction mass efficiency, process mass intensity, E-factor, and EcoScale, were evaluated for representative reactions to assess the material efficiency and waste profile of each protocol. This work provides a quantitative and balanced assessment of the SSC/Q-Tube approach for selective heterocycle synthesis.