A synthesis of 4-methylpyrano[2,3-e]indole-2,8,9-trione (5) is achieved from 7-amino-4- methylcoumarin by adopting the classical Sandmeyer methodology. The cyclocondensation reaction of pyrano-isatin 5 with the appropriately substituted o-phenylenediamines 6 in polyphosphoric acid proceeded regioselectively to furnish the respective pyrano[2’,3’:4,5]indolo[2,3-b]quinoxalines 7a - c. Structural assignments of the new compounds are based on microanalytical and spectral (IR, MS and NMR) data.
采用经典的桑德迈尔方法,从 7-氨基-4-甲基香豆素合成了 4-甲基吡喃并[2,3-e]吲哚-2,8,9-三酮(5)。在多磷酸中,吡喃异靛红 5 与适当取代的邻苯基二胺 6 发生环缩合反应,从而获得相应的吡喃并[2',3':4,5]吲哚并[2,3-b]喹喔啉 7a - c。