Fustero Santos, Román Raquel, Sanz-Cervera Juan F, Simón-Fuentes Antonio, Cuñat Ana C, Villanova Salvador, Murguía Marcelo
Departamento de Química Orgánica, Universidad de Valencia, E-46100 Burjassot, Spain.
J Org Chem. 2008 May 2;73(9):3523-9. doi: 10.1021/jo800251g. Epub 2008 Apr 10.
The preparation of N-methylpyrazoles is usually accomplished through reaction of a suitable 1,3-diketone with methylhydrazine in ethanol as the solvent. This strategy, however, leads to the formation of regioisomeric mixtures of N-methylpyrazoles, which sometimes are difficult to separate. We have determined that the use of fluorinated alcohols such as 2,2,2-trifluoroethanol (TFE) and 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) as solvents dramatically increases the regioselectivity in the pyrazole formation, and we have used this modification in a straightforward synthesis of fluorinated analogs of Tebufenpyrad with acaricide activity.
N-甲基吡唑的制备通常是通过合适的1,3-二酮与甲基肼在乙醇作为溶剂的条件下反应来完成。然而，这种策略会导致形成N-甲基吡唑的区域异构体混合物，有时难以分离。我们已经确定，使用氟化醇如2,2,2-三氟乙醇（TFE）和1,1,1,3,3,3-六氟-2-丙醇（HFIP）作为溶剂可显著提高吡唑形成中的区域选择性，并且我们已将此改进用于具有杀螨活性的四螨嗪氟化类似物的直接合成中。
