RESEARCH IN THE AZOLE SERIES .103. SYNTHESIS AND C-13 NMR-STUDY OF PYRAZOLE-4-CARBOXALDEHYDES

Ten new pyrazoles have been prepared and their C-13 nmr chemical shifts compared with those of twelve other pyrazoles, some of them prepared purposely for this study. The chemical shifts are discussed statistically assuming that they are additive. A formyl group in the position 4 of the pyrazole ring produces a large effect on carbon C4 (SCS = 17.3 ppm) and medium effects on carbons C3 (SCS = 1.9 ppm) and C5 (SCS = 3.8 ppm). The azines derived from pyrazole-4-carboxaldehydes are of the E,E-configuration.