in general and efficient syntheses of 6-acylcoumarins. Under standard Fries rearrangement conditions (7) undergo highly regioselective para-migration with aluminium chloride in nitromethane. The resulting C-acylated products (8) are converted into 6-acyl-7-methoxycoumarins (4). The scope and limitations of the rearrangement and the application to the total syntheses of the natural linear acylcoumarins
由7-甲氧基
香豆素以高收率制备的3-(2-酰氧基-4-
甲氧基苯基)
丙酸甲酯(7)是6-酰基
香豆素的一般和有效合成的关键中间体。在标准的炸薯条重排条件下(7)与
氯化铝在
硝基甲烷中进行高度区域选择性的对位迁移。将所得的C-酰化产物(8)转化为6-酰基-7-甲氧基
香豆素(4)。描述了重排的范围和局限性以及天然线性酰基
香豆素,geijerin(4a)和dehydrogeijerin(4b)在总合成中的应用。