Microwave-assisted minutes synthesis of bioactive phenylbutanoids occurring in Zingiber cassumunar

Microwave-assisted condensation of benzaldehyde (3a,b) with acetone in aqueous sodium hydroxide adsorbed on basic alumina provides phenylbutenone (4a-4b) in 68-71% yield within 4 min, which upon further reduction with sodium borohydride and basic alumina gives phenylbutenol (5a,b) in 91-94% yield within 2 min. Dehydration of 5 with anhydrous copper (H) sulfate gives phenylbutadiene (1a,b), a metabolite of Zingiber cassumunar, within 3 min in 42-48% yield, respectively. All the steps involve environmental friendly solvents and reagents, mild reaction conditions, and overall formation of product 1a,b from 3a,b in 34-38% yield within 9 min under microwave irradiation.