Reaction of Reformatsky reagents with 2,5-diphenyl-1,3,4-oxadiazole

The reaction of methyl a-bromoisobutyrate or 1-bromocycloalkanecarboxylates with zinc and 2,5-diphenyl-1,3,4-oxadiazole leads to 5-phenyl-2,4-dihydro-3H-pyrazol-3-one derivatives, with the cycloalkane series affording products of spiro structure. In the case of cyclobutane reactant, 3-phenyl-2,4,5,6-tetrahydropyrano[2,3-c]pyrazole is also formed.