A new route to 6-substituted 4a-e and 5,6-annulated 4f-l 1,2-benzisoxazoles has been developed through regioselective 1,2-nucleophilic addition of 5-lithiomethyl-3-methylisoxazole (2) to a variety of α-oxoketene dithioacetals 1a-l and subsequent cycloaromatization of the resulting hydroxyacetals in the presence of boron trifluoride -diethyl ether complex. The corresponding 4-dethiomethylated benzisoxazoles 6a-d were also synthesized by cyclocondensation of β- methylthio-α,β-unsaturated ketones with 2 under identical conditions. The reaction was further extended for the synthesis of (6-benzisoxazolyl)-substituted ethylenes 9a-e, butadienes 9f-g and hexatriene 9h by subjecting α-cinnamoyl ketene dithioacetals 7a-e and their higher enyl analogs 7f-h to similar transformations.
通过将 5-
硫代甲基-3-甲基
异噁唑(2)与多种δ-±-氧代酮二
硫代
乙醛 1a-l 进行 1,2-亲核加成,并随后在
三氟化硼-二
乙基醚络合物存在下对所生成的
羟基乙醛进行环芳基化,开发出了一条制备 6-取代型 4a-e 和 5,6-annulated 4f-l 1,2-苯并
异噁唑的新途径。在相同的条件下,δ-甲
硫基-δ,δ-不饱和酮与 2 环缩合,也合成了相应的 4-二
硫甲基化苯并
异噁唑 6a-d。通过使δ-肉桂酰基酮二
硫代
乙醛 7a-e 及其高烯基类似物 7f-h 发生类似的转化,该反应进一步扩展到合成(6-苯并
异噁唑基)取代的
乙烯 9a-e、
丁二烯 9f-g 和己
三烯 9h。