Synthesis of 2-(alpha-substituted N-tosylaminomethyl)-2,5-dihydrofurans byreaction of N-sulfonylimines with arsonium or sulfonium 4-hydroxyl-cis-2-butenylides

On treatment of N-tosylimines 1 and 4-hydroxyl-cis-butenyl arsonium salt 5 or sulfonium salt 11a with KOH in acetonitrile at room temperature, 2-(alph a-substituted N-tosylaminomethyl)-2,5-dihydrofurans 4 were obtained in mode rate yields through a new ylide cyclization process. Ylide 2 acts formally as an equivalent of the 2,5-dihydrofuran anion. However, the reaction of 4- hydroxyl-trans-butenyl sulfonium salt 11b with N-tosylimine 1b under the sa me conditions gave only the normal aziridinadon product 12. A plausible mec hanism was proposed for this new 5-membered cyclization reaction, and a hig h yield process for the synthesis of target molecules 4 is also recommended . (C) 2000 Elsevier Science Ltd. All rights reserved.