A Practical Preparation of Methyl 2-Methoxy-6-methylaminopyridine-3-carboxylate from 2,6-Dichloro-3-trifluoromethylpyridine.
作者:Tamaki HORIKAWA、Yoshimi HIROKAWA、Shiro KATO
DOI:10.1248/cpb.49.1621
日期:——
An effective and practical synthetic route to methyl 2-methoxy-6-methylaminopyridine-3-carboxylate (7), the key intermediate of 5-bromo-2-methoxy-6-methylaminopyridine-3-carboxylic acid (1), from 2,6-dichloro-3-trifluoromethylpyridine (12) was undertaken. Process improvements were highlighted by regioselectivity of 12 with a nitrogen nucleophile and conversion of the 3-trifluoromethyl group into the methoxycarbonyl group. The reaction of 12 with N-benzylmethylamine provided the 6-(N-benzyl-N-methyl)aminopyridine 26a and the regioisomer 26b in >98: <2 ratio in a quantitative yield. Treatment of 2-methoxy-6-methylamino-3-trifluoropyridine (14a) with a large excess of sodium methoxide followed by acid hydrolysis gave the pyridine-3-carboxylic ester 7 in an excellent yield. The potential application of this reaction is also described.
从2,6-二氯-3-三氟甲基吡啶(12)出发,采用有效且实用的合成路线,制备了2-甲氧基-6-甲基氨基吡啶-3-甲酸甲酯(7),它是5-溴-2-甲氧基-6-甲基氨基吡啶-3-甲酸(1)的关键中间体。12与氮亲核试剂的反应具有位点选择性,3-三氟甲基基团转化为甲氧羰基基团,这突出了工艺改进。12与N-苄基甲基胺的反应提供了6-(N-苄基-N-甲基)氨基吡啶26a和位点异构体26b,其比例大于98:小于2,且产率很高。用大量过量的甲醇钠处理2-甲氧基-6-甲基氨基-3-三氟吡啶(14a),然后进行酸水解,可以得到吡啶-3-羧酸酯7,且产率很高。还描述了这种反应的潜在应用。