Synthesis of α, β-unsaturated diketones and derivatives of Δ2-pyrazoline derived from 2, 5-diacetylthiophene

The Claisen reaction of 2, 5-diacetylthiophene with various aromatic and heterocyclic aldehydes was utilized to prepare 15 new unsaturated diketones(diarylidene-2, 5-diacetylthiophenes). Most of them were characterized as their bis-2, 4-dinitrophenylhydrazones, for which _max values in chloroform solution are given. The reaction of diarylidene-2, 5-diacetylthiophenes with phenylhydrazine. hydrochloride has given five 2, 5-bis(1-phenyl-5-R-²-pyrazoline-3-yl) thiophene showing strong luminescence. A method was developed for the synthesis of 2, 5-diacetylthiophene by the oxidation of 5-ethyl-2-acetothienone.