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

The Knoevenagel addition of aryl aldehydes 1 with nitroacetonitrile 2 in wa ter followed by dehydration of beta -nitroalcohols 3, allows (E)-2-aryl-1-c yano-1-nitroethenes 4 to be prepared by a one-pot procedure without using o rganic solvents. The reuse of the aqueous medium makes this process inexpen sive and highly environmentally friendly. The protocol was used to synthesi ze the benzo[b]pyrane [4,3-d][1,2]oxazine-2-oxide skeleton by a domino Knoe venagel-Diels-Alder process.