Facile and convenient synthesis of 4,4′-(arylmethylene)bis(1H-pyrazol-5-ols) by electrocatalytic tandem Knoevenagel-Michael reaction

An electrochemically induced catalytic tandem Knoevenagel-Michael reaction of two equivalents of 5-methyl-2-phenyl-2,4-dihydro-3H-pyrazol-3-one with various aromatic aldehydes in ethanol in an undivided cell in the presence of sodium bromide as an electrolyte results in the formation of the corresponding 4,4'-(arylmethylene)bis(1 H-pyrazol-5-ols) in 80-96% yields. The application of this efficient electrocatalytic method to the synthesis of biologically prominent 4,4'-(arylmethylene)bis(1H-pyrazol-5-ols) represents a facile and convenient approach to the realization of the tandem Knoevenagel-Michael reaction.