Polarized Ketene Dithioacetals; 55:<sup>1</sup>Synthesis of Novel 5-Aryl-2-methylthio-4<i>H</i>-pyran-4-ones from Cinnamoylketene Dithioacetals
作者:B. Deb、C. V. Asokan、H. Ila、H. Junjappa
DOI:10.1055/s-1987-28112
日期:——
A novel method for the synthesis of 5-aryl-2-methylthio-4H-pyran-4-ones 4a-h has been developed from the corresponding cinnamoylketene dithioacetals 1a-h in three successive steps. In the first step, 1a-h were oxidized with alkaline hydrogen peroxide to give the corresponding (β-aryl-,α,β-epoxypropanoyl)ketene dithioacetals 2a-h in 78-89% overall yields. In the second step the epoxyketones 2a-h were subjected to rearrangement in the presence of ether-boron trifluoride complex to give the corresponding (α-formyl-α-phenylacetyl)ketene dithioacetals 3a-h, which were then cyclized in the third step by refluxing in acetic acid/ethanol to afford the title compounds in good yields.
从相应的肉桂烯酮二硫代乙醛 1a-h 开始,分三个步骤合成了 5-芳基-2-甲硫基-4H-吡喃-4-酮 4a-h 的新方法。 第一步,用碱性过氧化氢氧化 1a-h,得到相应的(δ-芳基-,δ±,δ-环氧丙酰基)烯酮二硫代乙醛 2a-h,总产率为 78-89%。在第二步中,环氧酮 2a-h 在醚-三氟化硼络合物存在下进行重排,得到相应的(δ-甲酰基-δ-苯乙酰基)烯酮二硫代乙醛 3a-h,然后在第三步中通过在醋酸/乙醇中回流环化,以良好的收率得到标题化合物。