A new method for the synthesis of 4H-benzo [de]isoquinolin-4-ones has been developed, based on the reaction of 2-naphthyl ethers with an equimolar quantity of 1,3,5-triazines in polyphosphoric acid. With a 2.5 molar excess of 1,3,5-triazines in polyphosphoric acid, the products of 1,6-diacylation (diformylation) are formed. Isoquino[6¢,5¢,4¢:10,5,6]anthra [2,1,9-def]isoquinoline is formed upon reaction of a 1.5 molar excess of 1,3,5-triazine with naphthalene in polyphosphoric acid at 130-140°C.The monoacylation of naphthalene derivatives has already become a very well studied classic reaction. In contrast, there are few examples of the diacylation and diformylation of naphthalene derivatives. 1 It is well known that 1,3,5-triazine can undergo ring cleavage upon treatment with nucleophilic reagents and serve as a formyl group precursor. This property has been extensively used in organic synthesis. 2 Thus, formamidines, 2a perimidines, 2b benzimidazoles, 2b benzothiazoles, 2b benzoxazoles, 2b purines, 2b pyridines, 2c,d pyrimidines 2c,e,f and 1,6-naphthyridines 2g-i have been obtained utilizing different nucleophiles in reactions with 1,3,5-triazine (3a).Recently, we have reported the new reagent system of 1,3,5-triazines in polyphosphoric acid and have proved its effectiveness for the acylation and formylation of perimidine 3a,b and substituted naphthalenes, 3c and the peri-annelation of carbocyclic 3d and pyridine rings. 3e In the present paper we suggest methods for pyridine ring annelation to naphthalenes and regioselective 1,6-diacylation (diformylation) of 2-naphthyl ethers.On the basis of our previous work, 3 we propose that in the case of the reaction of 1,3,5-triazines with naphthalene and its monosubstituted derivatives, an intermediate 4 is formed, which is opened as for azanaphthalenes and in the series of subsequent transformations gives off the cation 7 (Scheme 1).The behavior of cations 7a-d depends on the nature of X. As a result of hydrolysis, dicarbonyl compounds (e.g., 8)or 4H-benzo [de]isoquinolin-4-ones 9a,b (if X = OR¢) may be formed (Scheme 2). Scheme 2 Hydrolysis of cations 7a-d