Ammonia → 7,7-Dimethyl-2-(isopropenyl)-6,7-dihydro-3 H,5H-pyrrolo[2,3-f]benzimidazol-6-one

Participants

Reaction Steps

3.0 g. (15.7 mmole) 5,6-diamino-3,3-dimethylindolin-2-one and 1.37 g. (15.9 mmole) methacrylic acid are heated for 30 minutes at 200° C. in 28 g. polyphosphoric acid. Thereafter, the reaction mixture is mixed with 40 ml. ice water. The brown suspension obtained is adjusted, while cooling with ice, to pH 8 with 45 ml. concentrated aqueous ammonia solution. The substance is filtered off with suction and washed with a little water. There are obtained 3.74 g. of crude product which are dissolved in 5 ml. dimethyl sulphoxide, diluted with 15 ml. methanol and purified over a silica gel column (7.50 g. gel; elution agent: dichloromethane/methanol 10:1 v/v). There is obtained 0.6 g. (14% of theory) of the title compound; m.p. 270°-273° C.

Provenance & Evidence