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Development of an Efficient Process to Prepare Methyl 4,5,6-Trichloropicolinate Using Highly Selective C–H Borylation/Chlorodeborylation Reactions
Organic Process Research & Development ( IF 3.1 ) Pub Date : 2022-10-11 , DOI: 10.1021/acs.oprd.2c00247
Xiaoyong Li 1 , Eric Wiensch 1 , Jossian Oppenheimer 2
Affiliation  

This report details the development of an efficient process to prepare methyl 4,5,6-trichloropicolinate using Ir-catalyzed C–H borylation followed by CuCl2-mediated chlorodeborylation under optimized conditions. The process featured extremely low loadings (as low as 0.0005 equiv) of an [Ir(OMe)cod]2 precatalyst with outstanding reactivity and regioselectivity (>150:1) during C–H borylation. The impurity from product dechlorination can be significantly reduced by >30-fold to <0.4%. The excellent reactivity and control of the protodeborylation impurity in subsequent copper-mediated chlorodeborylation was also highlighted. This enabled successful demonstration of a highly efficient process at a 46 mmol scale with an excellent overall yield (75%). Furthermore, it was showcased that the Ir catalyst and 4,4′-di-tert-butyl-2,2′-bipyridyl (dtbpy) ligand can be directly recycled and reused after filtration of the product. All these developments would offer significant economic benefits as well as process simplification for applying Ir chemistry.

中文翻译:

使用高选择性 C-H 硼酰化/氯去硼酸化反应制备 4,5,6-三氯吡啶甲酸甲酯的高效工艺开发

本报告详细介绍了在优化条件下使用 Ir 催化的 C-H 硼酸化,然后是 CuCl 2介导的氯代脱硼酸化制备 4,5,6-三氯吡啶甲酸甲酯的有效工艺的开发。该工艺的特点是 [Ir(OMe)cod] 2 的负载量极低(低至 0.0005 equiv)2在 C-H 硼化过程中具有出色反应性和区域选择性 (>150:1) 的预催化剂。产品脱氯产生的杂质可显着降低 >30 倍至 <0.4%。还强调了在随后的铜介导的氯代脱硼反应中对原脱硼杂质的优异反应性和控制。这使得在 46 mmol 规模上成功展示了一种高效工艺,具有出色的总产率 (75%)。此外,Ir催化剂和4,4'-二叔丁基-2,2'-联吡啶(dtbpy)配体可以在产品过滤后直接回收和重复使用。所有这些发展将提供显着的经济效益以及应用 Ir 化学的工艺简化。
更新日期:2022-10-11
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