Chemistry of Heterocyclic Compounds, Vol. 40, No. 10, 2004 REACTION OF 3-ACYLAMINO- AND 3-ALKOXYBENZO[c]PYRILIUM SALTS WITH HYDRAZINE S. L. Bogza 1 , S. Yu. Suikov 2 , N. M. Bogdan 2 , V. I. Dulenko 2 , and K. I. Kobrakov 1 The reaction of 3-acylamino- and 3-alkoxybenzo[c]pyrilium perchlorates with hydrazine has been studied. It was discovered that the direction of the recyclization of the pyran ring depends on the type of substituent in position 3 and on the ratio of reactants. Derivatives of isoquinoline and benzo-2,3- diazepine were obtained. Keywords: benzo-2,3-diazepine, benzo[c]pyrilium, hydrazine, isoquinoline, recyclization. In the whole variety of reactions of benzo[c]pyrilium salts with nucleophilic reagents that has been studied a limited number of works has been published on the interaction of them with hydrazine and its derivatives. It is known that benzo[c]pyrilium salts may be converted into derivatives of 2-aminoisoquinoline or benzo-2,3-diazepine [1-3]. Previously [4, 5] we reported conversions of benzo[c]pyrilium salts with functional substituents in position 4 (ester, cyano group) in the presence of hydrazine and phenylhydrazine, and certain factors determining the direction of recyclization. There are no data in the literature on analogous conversions of benzo[c]pyrilium salts containing functional substituents in position 3. The aim of the present work was to study the reactions of 3-acylamino-1-alkylbenzo[c]pyrilium salts 1 [6] and 3-alkoxy-1-alkylbenzo[c]pyrilium salts 2 [7] with hydrazine and also to search for new possibilities for obtaining nitrogen-containing heterocycles from them. The structure of the products of reacting salts 1 and 2 with hydrazine is regulated by the substituent at position 3 and by the salt–hydrazine ratio. On interacting perchlorates 1a,b and hydrazine hydrate in ratios from 1:1 to 1:3 the 1-alkyl-3-hydroxyisoquinolines 3 are formed, previously obtained by the action of ammonia [7]. Probably under these conditions the hydrazine molecule acts as a base and the oxonium cation, as in the case of the interaction with ammonia [7] and inorganic bases [8], undergoes an autorecyclization with the participation of the nitrogen atom of the acylamino group. An increase in the ratio to 1:5 leads to the formation of 1-alkyl-2- aminoisoquinolin-3(2H)-ones 4. Increasing the amount of nucleophile further does not affect the course of the reaction. Replacement of the acylamino group in position 3 by an alkoxy substituent changes the character of the conversions of the benzo[c]pyrilium cation. On interacting 1-alkyl-3-ethoxybenzo[c]pyrilium perchlorates 2a,b with an equimolar amount of hydrazine hydrate at room temperature, a mixture is formed of compound 4 and the ketoester hydrazone 5, but on heating only the isoquinolone 4 is obtained, which may be isolated both as the perchlorate and as the base. Compound 4 was also obtained in the reaction of salt 2 with hydrazine __________________________________________________________________________________________ 1 Moscow A. N. Kosygin State Textile University, Moscow 117983, Russia; e-mail: serge_zh@yahoo.com. 2 L. M. Litvinenko Institute of Physical Organic and Coal Chemistry, National Academy of Sciences of the Ukraine, Donetsk 83114. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No.10, pp. 1507-1511, October, 2004. Original article submitted March 5, 2002. 1300 0009-3122/04/4010-1300©2004 Springer Science+Business Media, Inc.