“…In 2017, our research group used 1,2,3‐thiadiazoles as the thioketene precursors by the treatment with base. We investigated the diastereoselective control in the (2+2) transannulation of 1,2,3‐thiadiazoles and imines [7] and annuloselectivity in the transannulation of 1,2,3‐thiadiazoles and imines [8] . Recently, we developed formal (3+3) transannulations of ethyl 1,2,3‐thiadiazole‐4‐carboxylates with conjugated alk‐2‐ynals and alk‐2‐enals, accessing six‐membered thiaheterocycles, 4 H ‐thiopyran‐4‐one and 2,3‐dihydro‐4 H ‐thiopyran‐4‐one derivatives, [9] respectively (Scheme 1b).…”