Development of Scalable Processes for the Preparation of <i>N</i>-Methyl-3-Bromo-5-Methyl Pyrazole
作者:Richard J. Fox、Chester E. Markwalter、Michael Lawler、Keming Zhu、Jacob Albrecht、Joseph Payack、Martin D. Eastgate
DOI:10.1021/acs.oprd.7b00091
日期:2017.5.19
The development and optimization of two scalable routes to N-methyl-3-bromo-5-methyl pyrazole is described. The initial Sandmeyer route entailed a three-step sequence from crotonitrile and methyl hydrazine, proceeding through the 3-amino pyrazole intermediate. Due to the GTI liability of the 3-amino pyrazole intermediate, a tedious steam-distillation, and <30% overall yield, we developed a second-generation
描述了开发和优化两种可扩展的路线,以N-甲基-3-溴-5-甲基吡唑。最初的桑德迈尔路线需要从巴豆腈和甲基肼开始进行三步操作,依次经过3-氨基吡唑中间体。由于3-氨基吡唑中间体的GTI责任,繁琐的蒸汽蒸馏以及<30%的总收率,我们开发了第二代不含巴氏剂的巴豆酸甲酯和甲基肼方法,该方法利用了缩合,溴化和氧化顺序。工艺开发导致改进了N-甲基-3-溴-5-甲基吡唑,具有更高的效率和更高的总收率。通过生成三氟甲磺酸盐大大改善了最终产品的分离,处理和存储,并且还讨论了盐的形式研究。