Thiopyrans and thiopyrylium salts from 1,5-diketones

Rapid access to polycyclic thiopyrylium compounds from unfunctionalized aromatics by thia-APEX reaction

“…2 One of the classical methods for synthesizing thiopyryliums is the annulative condensation reaction of 1,5-dicarbonyl with H 2 S in the form of Paal–Knorr synthesis. 1 c ,3 Thiopyrylium compounds can also be synthesized by reactions of arenethiols and 1,3-diketones or aminothioacrylamide derivatives with acids. 4 These methods are useful for constructing small π-conjugation systems such as thiopyrylium and benzothiopyrylium compounds.…”