BIFUNCTIONALIZED ALLENES. PART. X. AN ELECTROPHILIC CYCLIZATION PROTOCOL FOR CONVENIENT HIGHLY REGIOSELECTIVE SYNTHESIS OF 3-SULFONYLFURAN-2(5H)-ONES FROM 2-SULFONYLALLENOATES

A simple and convenient protocol for the highly regioselective synthesis of 3-sulfonylfuran-2(5H)-ones by electrophilic cyclization reaction of 2-sulfonylallenecarboxylates with neighbouring ester group participation is described. However, the reaction of 2-sulfonylalka-2,3-dien-1-ones with electrophilic reagents proceeded with formation of 2-sulfonylalka-2,4-dien-1-ones by addition-elimination reaction. A possible mechanism involving the cyclization and addition-elimination reaction of 2-sulfonyl-substituted allenic esters and ketones was proposed.