Regioselective Syntheses of Functionalized 2-Aminopyridines and 2-Pyridinones through Nucleophile-Induced Ring Transformation Reactions
作者:Atul Goel、Fateh V. Singh、Ashoke Sharon、Prakas R. Maulik
DOI:10.1055/s-2005-862365
日期:——
An efficient one-pot synthesis of 2-amino-6-aryl-4-methylsulfanylpyridines and 6-aryl-3-cyano-4-methylsulfanyl-2(1H)-pyridinone has been illustrated through ring transformation of 6-aryl-3-cyano-4-methylsulfanyl-2H-pyran-2-ones by urea through different reaction conditions. Various solvents and bases were employed to selectively prepare either 2-aminopyridines or 2-pyridinones. In case of direct fusion of 2H-pyran-2-one with urea in solvent-free conditions, both the products were obtained in 1:1 ratio, while the reaction in pyridine at reflux temperature exclusively afforded 2-aminopyridine in 80-90% yield. The reaction of 6-aryl-3-carbomethoxy-4-methylsulfanyl-2H-pyran-2-ones with urea at 150 °C afforded 2-pyridinone derivatives in good yield (70-80%).
通过不同的反应条件,利用尿素对6-芳基-3-氰基-4-甲基硫基-2H-吡喃-2-酮进行环转化,展示了一种高效的一锅法合成2-氨基-6-芳基-4-甲基硫基吡啶和6-芳基-3-氰基-4-甲基硫基-2(1H)-吡啶酮。采用多种溶剂和碱分别选择性地制备2-氨基吡啶或2-吡啶酮。在无溶剂条件下直接将2H-吡喃-2-酮与尿素熔融时,两个产品以1:1的比例获得,而在吡啶中加热回流反应则专门生成2-氨基吡啶,产率为80-90%。在150°C下,6-芳基-3-碳甲氧基-4-甲基硫基-2H-吡喃-2-酮与尿素反应生成的2-吡啶酮衍生物产率良好(70-80%)。