Regioselective Synthesis of Dihydrothiophene and Thiopyran Frameworks via Catalyst-Controlled Intramolecular Cγ/Cδ–S Fusion of α-Allyl-β′-oxodithioesters
摘要:
A highly efficient and atom-economic dual reaction manifold has been developed to synthesize 4H-thiopyran and 4,5-dihydrothiophene frameworks via regioselective intramolecular C-S fusion of alpha-allyl-beta'-oxodithioesters. The ring size of the sulfur-heterocycles has been efficiently tuned by the use of two different catalytic systems. Palladium activates the Cd-H of the allyl termini and facilitates the intramolecular C delta-S coupling to furnish six-membered thiopyran skeletons exclusively. Conversely, the allylic double bond of the same substrate has been activated by to promote the C delta-S cyclization leading to the formation of a five-membered dihydrothiophene nucleus.