Moyano E L, Yranzo G I
Instituto de Investigaciones Físicoquímicas de Córdoba (INFIQC), Departamento de Química Orgánica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, 5000 Córdoba, Argentina.
J Org Chem. 2001 May 4;66(9):2943-7. doi: 10.1021/jo001390a.
Flash vacuum pyrolysis (fvp) reactions of 1H-pyrazole (1), 3,5-dimethylpyrazole (2), and 3,5-diphenylpyrazole (3) were carried out over zeolites. Reactions were performed using ZCOY-7, NH(4)-Y, and Na-Y zeolites. Reaction temperatures of heterogeneous reactions were lower than the corresponding temperatures in the homogeneous system, showing a catalytic effect of the zeolites. Compounds 1-3 afforded nitrogen extrusion in homogeneous fvp reactions while in the heterogeneous ones different reactions were present. Compounds 1 and 2 also afforded nitrogen extrusion; products arising from ring fragmentation were found in reactions of 2 and 3 while an isomeric imidazole was isolated in reactions of 3. Isomerization of 3 is attributed to a transition-state selectivity by the catalyst due to the relation between the size of the molecule and the cavity of the zeolite. This isomerization reaction was present only when zeolites with active Brönsted sites were used.
在沸石上进行了1H-吡唑（1）、3,5-二甲基吡唑（2）和3,5-二苯基吡唑（3）的快速真空热解（FVP）反应。使用ZCOY-7、NH(4)-Y和Na-Y沸石进行反应。多相反应的温度低于均相体系中的相应温度，表明沸石具有催化作用。化合物1-3在均相FVP反应中发生氮的脱除，而在多相反应中则存在不同的反应。化合物1和2也发生了氮的脱除；在2和3的反应中发现了由环断裂产生的产物，而在3的反应中分离出了一种异构咪唑。3的异构化归因于催化剂的过渡态选择性，这是由于分子大小与沸石孔穴之间的关系。这种异构化反应仅在使用具有活性布朗斯特位点的沸石时出现。
