Cascade [4+1] annulation via greener nitrogen ylide in water: Synthesis of bicyclic and tricyclic fused dihydrofuran

Abstract

A novel imidazolium ylide activated [4+1] annulation approach is described for the diastereoselective synthesis of bicyclic and tricyclic fused dihydrofurans in water. This cascade annulation presumably proceeds via a Michael reaction triggered zwitterion enolate followed by concomitant intramolecular cylization. The methodology has distinction of being the first report on imidazolium ylide mediated [4+1] annulation in water as a unified greener approach involving in-situ base regeneration system and an alternative to pyridine ylide.