A Convenient Synthesis of 2,3‐Dihydro‐4 H ‐thiopyrano[2,3‐ b ]‐, ‐[2,3‐ c ]‐, or ‐[3,2‐ c ]pyridin‐4‐ones by the Reaction of the Corresponding 1‐(Chloropyridinyl)alk‐2‐en‐1‐ones with NaSH

2,3‐Dihydro‐4 H ‐thiopyrano[2,3‐ b ]pyridin‐4‐ones 4 were prepared by a three‐step sequence from commercially available 2‐chloropyridine ( 1 ). Thus, successive treatment of 1 with i Pr 2 NLi (LDA) and α , β ‐unsaturated aldehydes gave 1‐(2‐chloropyridin‐3‐yl)alk‐2‐en‐1‐ols 2 , which were oxidized with MnO 2 to 1‐(2‐chloropyridin‐3‐yl)alk‐2‐en‐1‐ones 3 . The reactions of 3 with NaSH⋅ n H 2 O proceeded smoothly at 0° in DMF to provide the desired thiopyranopyridinones. Similarly, 2,3‐dihydro‐4 H ‐thiopyrano[2,3‐ c ]pyridin‐4‐ones 8 and 2,3‐dihydro‐4 H ‐thiopyrano[3,2‐ c ]pyridin‐4‐ones 12 were obtained starting from 3‐chloropyridine ( 5 ) and 4‐chloropyridine ( 9 ), respectively.