Polarized Ketene Dithioacetals; 53:<sup>1</sup>A Facile Synthesis of 2-Aryl-6-methylthio-4<i>H</i>-pyran-4-ones and a Novel Cycloaromatization Reaction
作者:L. W. Singh、H. Ila、H. Junjappa
DOI:10.1055/s-1987-28107
日期:——
A facile route to hitherto unreported 2-aryl-6-methylthio-4H-pyran-4-ones 4a-f has been developed by base-catalyzed condensation of acylketene dithioacetal 2 with substituted methyl benzoates 1a-f followed by subsequent ring closure of resulting α-aroylacylketene dithioacetals 3a-f. Acylketene dithioacetal 2 and the corresponding β-methylthioenone 9 are shown to undergo self-condensation and aromatization in the presence of sodium hydride and methylbenzoate in refluxing xylene to give 2, 6-bis(methylthio)-4-hydroxy-acetophenone (6) and 4-hydroxyacetophenone (10) respectively in good yields. A mechanistic pathway for the formation of 6 and 10 via 3 has been described.
一种简单的合成路线被开发出来,能够合成迄今未报道的 2-芳基-6-甲硫基-4H-吡喃-4-酮 4a-f。这一过程是通过以碱催化的方式,将酰基乙烯基二硫代乙酰缩合物 2 与取代的甲基苯酸酯 1a-f 反应,并随后对得到的 α-芳酰基酰基乙烯二硫代乙酰缩合物 3a-f 进行环闭合。酰基乙烯基二硫代乙酰缩合物 2 和相应的 β-甲基硫酮 9 被证明在氢化钠和甲基苯酸酯的存在下,在回流的二甲苯中自我缩合并芳香化,分别以良好的产率生成 2, 6-双(甲基硫基)-4-羟基-乙酰苯酮 (6) 和 4-羟基-乙酰苯酮 (10)。阐述了通过 3 形成 6 和 10 的机制路径。