Catalyst-free green synthesis of tetrahydro-benzo[b]pyrans in magnetized water: experimental aspects and molecular dynamics simulation

In this work, magnetized water is applied as a green-promoting medium for the catalyst-free, one-pot, practical, efficient, and environmentally benign multi-component synthesis of tetrahydrobenzo[b]pyrans. Some tetrahydrobenzo[b]pyran derivatives are synthesized by a three-component reaction of an aldehyde, malononitrile, and 1,3-cyclohexanedione or 5,5-dimethyl-1,3-cyclohexanedione at room temperature. This method offers the advantages of short reaction time, low cost, quantitative yield, simple work-up, and no need for an organic solvent. It is thus enviro-economic with no dangerous wastes produced. The molecular insight on the system shows that magnetized water has a dramatic effect on the strength of the interactions between all organic reagents as well as an increase of a factor of 1.2 in order of the number of hydrogen bonds between water and each organic reagent. In the presence of magnetized water, the reagents are more condensed in the center of the simulation box, showing a more considerable molecular interaction leading to a more viscous system that limits the species movements.