Facile synthesis of sulfenyl-substituted isocoumarins, heterocycle-fused pyrones and 3-(inden-1-ylidene)isobenzofuranones by FeCl ₃-promoted regioselective annulation of o-(1-alkynyl)benzoates and o-(1-alkynyl) heterocyclic carboxylates with disulfides

Reported herein is the FeCl ₃-promoted intermolecular sulfoesterification of o-(1-alkynyl)benzoates with disulfides, which provides a convenient and efficient method for synthesis of 4-sulfenylisocoumarins. Various functional groups such as methoxy, halides, ester, cyano and silicon groups in the substrates are tolerated, and heterocycle-fused chalcogenylpyrones are also successfully achieved directly from the corresponding heterocyclic precursors under the same reaction conditions. In addition, starting from diynylbenzoate, this reaction sequence can be combined with a bicyclization step leading to the tetracyclic (E)-3-(2-phenyl-3-phenylchalcogenylinden-1-ylidene)isobenzofuranone frameworks with high regiospecificity and exclusive trans stereoselectivity.