Base-mediated [4+2] annulation of electron-deficient nitrobenzoheterocycles and α,α-dicyanoalkenes in water: Facile access to structurally diverse functionalized dibenzoheterocyclic compounds
A base-mediated [4 + 2] annulation of 2-nitrobenzofurans, 2-nitrobenzothiophenes, 3-nitrobenzothiophenes, and 3-nitroindoles with α,α-dicyanoalkenes for the synthesis of structurally diverse dibenzoheterocyclic compounds was developed. The reaction proceeded smoothly via a tandem vinylogous Michaeladdition/cyclization/tautomerization/elimination process in water with cesium carbonate as base, affording