Synthesis of 2-(α-Substituted N-Tosylaminomethyl)-2,5-Dihydrofurans by Reaction 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-(α-substituted N-tosylaminomethyl)-2,5-dihydrofurans 4 were obtained in moderate 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 same conditions gave only the normal aziridination product 12. A plausible mechanism was proposed for this new 5-membered cyclization reaction, and a high yield process for the synthesis of target molecules 4 is also recommended.