CONJUGATED AZOALKENES .11. DIRECT SYNTHESIS OF SUBSTITUTED PYRAZOLES AND 4-TRIPHENYLPHOSPHORANYLIDENE-4,5-DIHYDROPYRAZOL-5-ONES BY HETEROCYCLIZATION OF SOME ZWITTERIONIC 1,4-ADDUCTS BETWEEN CONJUGATED AZOALKENES AND TRIPHENYLPHOSPHINE

The simple and direct synthesis in good yields of substituted pyrazoles and 4-triphenylphosphoranylidene-4,5-dihydropyrazol-5-ones is reported. These products have been prepared by heterocyclization under different reaction conditions of some 1,5-zwitterionic species obtained from the 1,4-conjugate addition of triphenylphosphine to the azo-ene system of conjugated azoalkenes.