E. V. Kuznetsov

2-benzopyrylium salts. 33. 4-1′-Dimerization of 2-benzopyrylium salts. Formation of benz [a] anthracenes

The conversion of 2-benzopyrylium salts to benz [a] anthracenes, which proceeds through prior dimerization of a new type, was observed. An intermediate dimer was isolated, its properties were studied, and assumptions regarding the mechanisms of its formation and conversion to benz [a] anthracenes, cenes were expressed.

2-Benzopyrylium salts

Abstract2-Veratryl-5,6-dimethoxyindanone and 2-veratrylindane-1,3-dione, respectively, were obtained by intramolecular acylation ofα,β-diveratrylpropionic acid and condensation of veratraldehyde with phthalide in strongly alkaline media. A method was worked out for the synthesis of indeno[1,2-c]-2-benzopyrylium salts, from which indeno[1,2-c]isoquinolines are formed in good yields.

2-Benzopyrylium salts. 26. Recyclization of 2-benzopyrylium salts to ?-naphthols

The behavior of 2-benzopyrylium salts with a CH2 group in the 1 position at pH ⩽ 7 was studied, and it was established that they undergo recyclization to α-naphthols under these conditions. A mechanism for the conversion is proposed. One of the intermediates, viz., 3-hydroxy-1-tetralone, was isolated.

2-Benzopyrylium salts. 39. Recyclization of 2-benzopyrylium salts upon reaction with vinyl ethyl ether and compounds with an active methylene group

The reaction of 2-benzopyrylium salts with vinyl ethyl ether, ethyl acetoacetate, malonodinitrile, and nitromethane gives variously substituted naphthalene derivatives. It is proposed that the reaction with vinyl ether proceeds through [4+2] cycloaddition, while the reaction with the compounds with an active methylene group proceeds either through the ANRORC mechanism or through the formation of bridged intermediates, depending on the conditions.

2-Benzopyrilium salts. 30. Synthesis and properties of 2-benzopyrilium salts with the 2,6-di-t-butylphenyl substituent in position 3

We achieved the synthesis of 2-benzopyrilium salts with a 2,6-di-t-butylphenyl substituent in position 3 by acylation of 3,5-di-t-butyl-4-hydroxy-3′,4′-dimethoxydesoxybenzoin. We carried out a comparison of the concurrent deprotonation of 1-methylene and hydroxyl groups in these salts and obtained the corresponding isoquinoline bases.

2-Benzopyrylium salts. 27. Formation of substituted chrysenes from 1-methyl-2-benzopyrylium salts

Abstract1-Methyl-2-benzopyrylium salts with a free β position of the heteroring primarily form substituted chrysenes. In alkaline media this process does not proceed through the intermediate formation of 1,5-diketones.

2-Benzopyrylium salts. 24. Synthesis and reactions of 3-(2-methylenecarboxyaryl)-2-benzopyrylium salts with amines

Abstract5-Oxoniachrysene and N-methylisoquinolinium perchlorates and substituted 1-naphthylamines were synthesized on the basis of 1-R-3-(2-methylenecarboxyaryl)-2-benzopyrylium salts.

Synthesis of ?-pyrones, flavones, and isocoumarins by destructive oxidation of pyranylidenes and their benzo analogs

Preparative methods for the synthesis of isocoumarins, γ-pyrones, and flavones by destructive oxidation of methylenepyrans with potassium permanganate in acetone were developed.

2-Benzopyrylium salts. 44. Formation of 4-acyl-3,4-dihydroisoquinolinium salts from the reaction of 2-benzopyrylium salts with azomethines and the cycloaddition of male-imides to the product of their deprotonation, the 2,3-dihydroisoquinolines

The effect of substituents in the 2-benzopyrylium cation and in the azomethines on the character of their reaction in various solvents has been clarified. It was shown that the 4-acyl-3,4-dihydroisoquinolinium salts resulting after deprotonation form compounds with an ortho-quinonoid structure which then react with maleimides by cycloaddition.

2-Benzopyrylium salts. 36. Disproportionation of 2-benzopyrylium salts through prior 4-1′ dimerization

It was observed that the disproportionation of 2-benzopyrylium salts proceeds through prior dimerization. Intermediates were isolated and identified. Assumptions regarding the mechanism of the transformation are expressed.