Multicomponent domino reactions of acetylenedicarboxylates: divergent synthesis of multi-functionalized pyrazolones and C-tethered bispyrazol-5-ols

An efficient and practical methodology of selectively divergent synthesis of arylidene pyrazolones and C-tethered bispyrazol-5-ols via multicomponent domino reactions of acetylenedicarboxylates, phenylhydrazine and aromatic aldehydes has been developed. The electron-donating aryl groups (EDAG)-attached aldehydes resulted in the pyrazolone skeleton, whereas the electron-withdrawing aryl groups (EWAG) led to the C-tethered bispyrazol-5-ols with simultaneous formation of two new pyrazole rings.