Flash Vacuum Pyrolysis (FVP) over Solid Catalyst. Part II: Pyrazoles over Hydrotalcites

ELIZABETH L. MOYANO; MARGARITA DEL ARCO; VICENTE RIVES; GLORIA I. YRANZO

JOURNAL OF ORGANIC CHEMISTRY

AMER CHEMICAL SOC

Año: 2002 vol. 67 p. 8148 - 8150

0022-3263

Flash vacuum pyrolysis (fvp) reactions of NH-pyrazole (1) and 3,5-diphenylpyrazole (2) wereinvestigated in the presence of anionic clays having hydrotalcite structure (HT). Solid catalystswith Mg:Al ratio equal to 2:1 containing carbonate (HT-1), nitrate (HT-2), and silicate (HT-3) asinterlayer anions were employed. Between 400 and 600 °C, compound 1 remained almost unchanged and only unidentified volatile products were detected in small amounts. In contrast, 2 afforded benzonitrile (3) and phenylacetonitrile (4) by a ring fragmentation reaction at 450 °C. At a higher temperature (660 °C), the same products obtained in homogeneous fvp reactions, i.e., 2-phenylindene (5) and 3-phenylindene (6), were obtained showing no catalysis by HT under these conditions.Results showed that the yield is strongly dependent on the nature of the interlayer anion in thehydrotalcite structure. In comparison with reactions of 2 over zeolites, HTs exhibit selectivity forring fragmentation reaction.