Continuous Flow Synthesis of 2H‐Thiopyrans via thia‐Diels–Alder Reactions of Photochemically Generated Thioaldehydes

Herein, we report a novel protocol for the photochemical generation of thioaldehydes in a continuous flow process which were in situ reacted with electron rich 1,3‐butadienes in thia‐Diels–Alder reactions. A broad range of 3,6‐dihydro‐2H‐thiopyrans were formed as products in much higher yields and productivities as compared to classical batch processes. Moreover, greatly reduced reaction times and a facile large‐scale preparation of products were achieved by fully exploiting the advantages of continuous flow technology.