NEW MATERIAL:6,14-Dihydro-5H-pyrido[1',2':1,2]pyrimido[4,5-b]acridine-7,15- dione of formula I. USE:An intermediate for preparing pigments. 5H-Pyrido [1',2':1,2,]pyrimido [4,5-b] acridine-7,15-dione useful as red pigments can be obtained by dehydrogenation and oxidation of the cyclohexadiene ring. PROCESS:An 2-anilino-1,4-dihydro-9-acridanone-3-carboxylic ester of formula II: (Et is ethyl or may be other alkyl group) is reacted with 2-aminopyridine of formula III in a liquid medium, e.g. benzene, in the presence of an acid catalyst, e.g. sulfuric or hydrochloric acid, at 80-200 deg.C for about 3 hr or longer under heating to effect the amino group exchange and intramolecular ring closure. The desired compound of formula I can be thus obtained.
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