Water, a clean, inexpensive, and re-usable reaction medium. One-pot synthesis of (E)-2-aryl-1-cyano-1-nitroethenes

Abstract

The Knoevenagel addition of aryl aldehydes 1 with nitroacetonitrile 2 in water followed by dehydration of β-nitroalcohols 3, allows (E)-2-aryl-1-cyano-1-nitroethenes 4 to be prepared by a one-pot procedure without using organic solvents. The reuse of the aqueous medium makes this process inexpensive and highly environmentally friendly. The protocol was used to synthesize the benzo[b]pyrane [4,3-d][1,2]oxazine-2-oxide skeleton by a domino Knoevenagel–Diels–Alder process.