A green and highly efficient method has been developed for the one-pot synthesis of tetrahydrobenzo[b]pyrans via a three-component condensation of aldehydes, 1,3-cyclic diketones, and malononitrile under MW irradiation without using any catalyst and solvent. This transformation presumably occurs by a sequential Knoevenagel condensation, Michael addition, and intramolecular cyclization. Operational simplicity, solvent and catalyst-free conditions, the compatibility with various functional groups, nonchromatographic purification technique, and high yields are the notable advantages of this procedure.
Pyrazolo[3,4-b]pyridines derivatives have been synthesized via one-pot condensation of 3-methyl-1-phenyl-1H-pyrazolo-5-amine (1), paraformaldehyde (2) and β-diketones (3) under microwave irradiation in aqueous media catalyzed by InCl3.
Herein a versatile HOTf-catalyzed and solvent-free system for highly efficient one-pot synthesis of privileged benzene and pyridine derivatives has been developed using ketones and ketones with amines as simple substrates, respectively.
Microwave-Assisted Three-Component “Catalyst and Solvent-Free” Green Protocol: A Highly Efficient and Clean One-Pot Synthesis of Tetrahydrobenzo[b]pyrans