First synthesis of ferrocenyl-substituted thiochalcones and their [4+2]-cycloadditions with acetylenic dienophiles

Ferrocenyl methyl ketone reacts with aromatic aldehydes yielding 1-ferrocenyl-3-aryl-propenones (chalcones), which upon treatment with Lawesson’s reagent (LR) are converted to the corresponding thiochalcones. The latter enter the thia-Diels–Alder reaction with acetylenic dienophiles (DMAD and methyl propiolate) to give ferrocenyl-substituted 4H-thiopyrans. In the case of methyl propiolate, the formation of the six-membered ring occurs with complete regioselectivity.