Synthesis of thiophene analogs of 1, 3, 5-triphenylpyrazoline derivatives

Nineteen ²-pyrazolines hitherto undescribed in the literature are prepared by reacting thiophene and selenophene analogs of chalcones with phenylhydrazine or p-nitrophenylhydrazine. It is shown that thiophene and selenophene chalcones can be more easily cyclized than their furan analogs. The 2, 4, 6-trimethoxy group when present in the 1-(thienyl-2)-3-arylpropenone-1 molecule causes steric hindrance in the corresponding pyrazoline.