Chemistry of Heterocyclic Compounds, Vol. 29, No. 11, 1993 REACTIONS OF FUNCTIONALLY SUBSTITUTED BENZO[c]PYRYLIUM SALTS. SYNTHESIS OF 5H-BENZO-2,3- DIAZEPINES S. L. Bogza and Yu. A. Nikolyukin 5H-Benzo-2,3-diazepine derivatives are formed in the reaction of 4-ethoxycarbonylbenzo[c]pyrylium perchlorates with excess hydrazine hydrate. It was established that the key intermediate in the reaction is the 2-aminoisoquinolinium cation. A method for the recyclization of 4-cyanobenzo[c]pyrylium salts to 5H-benzo- 2, 3-diazepine derivatives was found. We have previously reported the synthesis of benzo[c]pyrylium derivatives with functional substituents in the heterocyclic part of the molecule [1] and demonstrated, in the case of transformations of 4-cyanobenzo[c]pyrylium perchlorates, that the introduction of an electron-acceptor substituent into the benzo[c]pyrylium cation substantially expands the spectrum of its transformations in reactions with nucleophiles. We have observed that the recyclization of 1,3-dialkyl-4-cyano-6,7- dimethoxybenzo[c]pyrylium salts by the action of excess hydrazine hydrate to 2-amino-4-cyanoisoquinolinium derivatives is accompanied by replacement of the 6-methoxy group by a hydrazine residue [2]. The new pyrazolo[5,4-c]isoquinoline heterocyclic system is formed under the same conditions from 1-methyl-3-phenyl-4-cyanobenzo[c]pyrylium salts [3]. In the present paper we give the results of a study of the transformations of 4-ethoxycarbonylbenzo[c]pyrylium derivatives with hydrazine hydrate, as well as a new pathway for the recyclization of 4-cyanobenzo[c]pyrylium salts. Replacement of the cyano group in the 4 position of the benzo[c]pyrylium cation by an ester substituent completely changes the recyclization pathway. Compounds with nonionic character are formed by the action of excess hydrazine hydrate on 4-ethoxycarbonylbenzo[c]pyrylium perchlorates Ia, b. The spectral-analytical characteristics make it possible to propose the 5H-benzo-2,3-diazepine structure for IIa, b. The IR spectrum of 5-hydrazinocarbonyl- 1,4-dimethyl-7,8-dimethoxy-5H-benzo-2,3-diazepine (IIa) contains absorption bands of primary (3400, 3350 cm-I) and secondary (3290 cm-1) amino groups, a carbonyl group (1660 cm-1), and C=N and C=C bonds of the heteroring and the benzene ring (1590-1635 cm-1). In addition to singlets of methyl and methoxy COOC2H5 CONHNH2 C H 3 0 ~ R ff ;T R , equiv. NH2NH 2 . ~ L _>N CH O/~ ~//O 3 - T c, o4- ",F N CH3 NHzNH2 CH3 l a, b ~ lequiv. ~ ~ n,a,b COOC2H5 CH30~ ~+~ CH3 CH30" v -,~//N'NH 2 CH3 111 ClO 4- I--II a R= CH3, b R = Ph Institute of Physical Organic Chemistry and Coal Chemistry, Academy of Sciences of Ukraine, Donetsk 340114. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1475-1477, November, 1993. Original article submitted October 13, 1993. 1268 0009-3122/93/2911-1268512.50 9 Plenum Publishing Corporation