Sulfuric Acid → 5,11-Dihydro-9-methyl-6H-pyrido[2,3-b][1,4]benzodiazepin-6-one

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Reaction Conditions

Reaction Steps

127.0 g (0.485 mol) of 2-amino-N-(2-chloro-pyridin-3-yl)-4-methyl-benzamide (m.p. 150°-152° C.) prepared analogously to Example A from 2-chloro-3-amino-pyridine and methyl 2-amino-4-methyl-benzoate (see F. Mayer and R. Schulze, Ber. Dtsch. Chem. Ges. 58, 1465 [1925]) were suspended in 500 ml of sulpholane and after the addition of 1.4 ml of conc. sulphuric acid the suspension was heated for 3 hours to 130° C. with stirring. It was then left to cool to 80° C., 500 ml of toluene were added and the mixture was left to stand overnight at ambient temperature. The crystals formed were suction filtered, suspended in 0.75 liters of dichloromethane, suction filtered once more and thoroughly washed with dichloromethane. After drying in a circulating air dryer, 70.2 g (64% of theory) of very slightly yellow crystals were obtained, m.p. 286°-288° C., which were further reacted without any further purification.

Provenance & Evidence