Epoxides of some pyrazolylprop-2-en-1-ones and their reactions

Pyrazolylprop-2-en-1-ones of the type R1CHCH·COR2 and R1CO·CHCHR2(R1= aryl and R2= 1-phenyl-pyrazol-4-yl) have been prepared, and their epoxidation with t-butyl hydroperoxide or alkaline hydrogen peroxide has been studied. Epoxy-ketones are produced when the vinyl group is adjacent to the aryl group but not when it is adjacent to the pyrazolyl group. t-Butyl peroxide gave the best yields of epoxy-ketone; alkaline hydrogen peroxide also caused fission at the double bond and/or rearrangement of the epoxy-ketone to an α-hydroxypropionic acid derivative. The epoxides did not undergo acid-catalysed rearrangement to give propane-1,3-diones, but gave the fission products, 4-hydroxyacetyl-1-phenylpyrazole and an aldehyde.