New reactivity patterns in the Diels–Alder reactivity of nitrobenzofuroxans
†
Abstract
The reaction of cyclopentadiene with 4-nitro-6-trifluoromethylsulfonylbenzofuroxan 5 in dichloromethane or chloroform proceeds stereoselectively at 0 °C to afford a single compound 6, which is shown to result from an inverse electron-demand Diels–Alder condensation involving the carbocyclic ring of 5 as the diene contributor. However, the adduct 6, whose X-ray structure could be obtained, is not the thermodynamically stable product of the interaction. Keeping a solution of 6 at room temperature results after a few days in the isolation of a new adduct 7a which arises from a regioselective and stereoselective normal electron-demand Diels–Alder condensation involving the C(4)C(5) double bond of 5 as the dienophile contributor. The carbodienic behaviour of 5 as well as the preferred dienophilic reactivity of the C(4)C(5) rather than of the C(6)C(7) double bond, represent two new reactivity patterns in the chemistry of the nitrobenzofuroxans.
Please wait while we load your content...
