Syntheses of 1-substituted furan-fused 3-sulfolenes and their Diels–Alder reactions
Abstract
The preparation of 1-substituted 4H,6H-dihydrothieno[3,4-c]furan 5,5-dioxides and their intermolecular Diels–Alder reactions with typical dienophiles are described. 1-Acetyl-1d and 1-nitro-furansulfolene 1e were prepared by simple new methods. Acetyl and nitro substituents in the furan moiety did little to diminish its Diels–Alder reactivity relative to the corresponding furans. Furthermore, on reaction with dimethyl fumarate, 1-acetylfuransulfolene 1d acted like the corresponding 3,4-dimethylenefuran.