O-Phenylenediamine → 2-(3,3-Dimethyl-2,3-dihydro-2-oxo-(1H)-6-indolyl)benzimidazole

Participants

Reaction Steps

One heated 3,3-dimethyl-2,3-dihydro-2-oxo-(1H)-6-indolecarbonitrile (2.6 g, preparation described in DE-A-3,818,830) and ortho-phenylenediamine (2.6 g) in polyphosphoric acid for 6 h at 160° C. One allowed to cool to 80°-90° C., added ice thereto, diluted with water to a volume of 1.2 l and neutralised with conc. ammonia. One extracted with a mixture of dichloromethane:methanol=10:1, removed the solvent in a vacuum and purified the residue column chromatographically (silica gel 60, dichloromethane:methanol. ammonia=20:1). One obtained 0.4 g of grey crystals which one recrystallised from ethanol/water. One obtained 195 mg of the title compound with the m.p. 326°-330° C.

Provenance & Evidence