Syntheses of 6-acylcoumarins via highly regioselective fries rearrangements. Total syntheses of the linear acylated coumarins geijerin and dehydrogeijerin.
作者:Nicholas Cairns、Laurence M. Harwood、David P. Astles
DOI:10.1016/s0040-4020(01)90370-9
日期:1992.9
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。