Synthesis of 2-amino-7-hydroxy-4H-chromene derivatives under ultrasound irradiation: A rapid procedure without catalyst

AbstractA highly efficient three-component synthesis of 2-amino-7-hydroxy-4H-chromenes by one-step condensation of aldehydes with malononitrile and resorcinol without catalyst in water under ultrasonic irradiation is described. This implies a convenient route avoiding the usage of hazardous organic solvents. The versatility of this method was checked by employing various aldehydes (acyclic, aromatic and heteroaromatic) which showed reasonable yields of chromene derivatives under ultrasound irradiation. Compared with conventional methods, the main advantages of the present procedure are its being a green method, its milder conditions, necessary shorter reaction time, and its higher yields and selectivity without the need for a transition metal or base catalyst