AlCl₃-Promoted Intramolecular Indolinone-Quinolone Rearrangement of Spiro[indoline-3,2-quinoxaline]-2,3-diones: Easy Access to Quinolino[3,4-b]quinoxalin-6-ones

A facile and direct intramolecular indolinone-quinolone rearrangement was developed for the synthesis of quinolino[3,4-b]quinoxalin-6-ones from spiro[indoline-3,2 '-quinoxaline]-2,3 '-diones, which are readily available with use of isatines, malononitrile, and 1,2-phenylenediamines under quite mild conditions. This efficient approach provides excellent yields and could potentially be used for the construction of a diverse library of quinolino[3,4-b]quinoxalin-6-ones for high-throughput screening in medicinal chemistry. The reaction mechanism is explored by extensive DFT calculations.