Photochemical synthesis of 4-ethoxycarbonyl-5-hydroxypyrazoles

Abstract

The photochemical decomposition of 4-ethoxycarbonyl-5-diazopyrazoles in tetrafluoroboric acid results in corresponding 4-ethoxycarbonyl-5-hydroxypyrazoles (V-VII). The irradiation of the diazocompound in dioxane, toluene or tetrahydrofurane proceeds with a reductive decomposition producing corresponding 4-ethoxycarbonylpyrazole (VIII) as the main photoproduct.