A. A. Aleksandrov

Synthesis and some transformations of 2-(2-thienyl)-1(3)H-imidazo[4,5-f] quinoline

Abstract2-(2-Thienyl)-1(3)H-imidazo{cm[4,5-f]}quinoline was synthesized by the Weidenhagen reaction of quinoline-5,6-diamine with thiophene-2-carbaldehyde. Its methylation in the system KOH-DMSO gave isomeric 1-methyl-2-(2-thienyl)-1H- and 3-methyl-2-(2-thienyl)-3H-imidazo{cm[4,5-f]}quinolines, the latter being the major product. The 3-methyl derivative was subjected to electrophilic substitution reactions (bromination, nitration, formylation, acylation, sulfonation). Depending on the conditions, electrophilic attack was directed at the thiophene or quinoline fragment or both these.

Synthesis and properties of 1-methyl-2-phenyl-5-(2-furyl)- and 1-methyl-2-phenyl-5-(2-thienyl)imidazoles

Abstract2-Phenyl-5-(2-furyl)- and 2-phenyl-5-(2-thienyl)imidazoles were synthesized by condensation of 2-furoylmethyl and 2-thenoylmethyl acetates with benzaldehyde under the conditions of Weidenhagen reaction. The products were converted to N-methyl derivatives in the KOH-acetone system. The electrophilic substitution reactions of the products (acylation, bromination, nitration, sulfonation, hydroxymethylation) were studied.

2-(2-Furyl)-1(3)H-imidazo[4,5-f]quinoline. Synthesis and electrophilic substitution reactions

Abstract2-(2-Furyl)-1(3)H-imidazo[4,5-f]quinoline was synthesized by the Weidenhagen reaction of quinoline-5,6-diamine with furfural. Its alkylation with methyl iodide in the system KOH-DMSO gave two isomeric N-methyl derivatives, 2-(2-furyl)-1-methyl-1H- and 2-(2-furyl)-3-methyl-3H-imidazo[4,5-f]quinolines, the latter prevailing. 2-(2-Furyl)-3-methyl-3H-imidazo[4,5-f]quinoline was brought into electrophilic substitution reactions: bromination, nitration, formylation, acylation, sulfonation. Depending on the reaction conditions, electrophilic attack could be directed at both furan ring and quinoline fragment.

Synthesis and properties of 2-(2-furyl)-and 2-(2-Thienyl)-1,3-benzoxazoles

Condensation of o-aminophenol with furoyl and thenoyl chlorides in 1-methylpyrrolidin-2-one gave, respectively, 2-(2-furyl)- and 2-(2-thienyl)-1,3-benzoxazoles in which the furan and thiophene rings showed no acidophobic properties. Reactions of 2-(2-furyl)- and 2-(2-thienyl)-1,3-benzoxazoles with electrophilic reagents (acylation, bromination, nitration, and sulfonation) afforded products of hydrogen replacement in both hetaryl and benzene rings, depending on the conditions.

Synthesis of novel fluorescent 2,5-di(benzimidazol-2-yl) derivatives of furan, thiophene, selenophene, and 2,4-di(benzimidazol-2-yl)pyrrole

Investigation of electronic and spectral properties of furyland thienylbenzazoles has shown that 2,5-di(benzimidazol-2-yl)derivatives of five-membered heterocycles with one heteroatom are promising from the viewpoint of requirements to fluorescent dyes and biological fluorescent probes. In the present work, we synthesized the 2,5-dibenzimidazolyl derivatives of furan, thiophene, selenophene and pyrrole.

Oxidation products of fused 2-hetarylimidazole derivatives

Oxidation of 5-(1-methyl-1H-benzimidazol-2-yl)thiophene-, and -selenophene-2-carbaldehydes with potassium dichromate in 20% aqueous sulfuric acid afforded the corresponding carboxylic acids. Analogous reaction with 5-(1-methyl-1H-benzimidazol-2-yl)furan-2-carbaldehyde led to the formation of 1-methyl-1H-benzimidazole as a result of decarboxylation of the primary oxidation product and subsequent decomposition of the furan ring. Probable factors responsible for instability of 5-(1H-benzimidazol-2-yl)-hetarene-2-carboxylic acids were considered. The oxidation of 2-furylnaphtho[2,3-d]- and 2-hetarylphenanthro-[9,10-d]imidazoles gave, respectively, an anthraquinone analog and 6,7-quinones. π-Electron-rich heterocycles in 2-furyl- and 2-pyrrolylphenanthro[9,10-d]imidazoles were oxidized completely, being replaced by hydrogen.

Synthesis and Some transformations of trans-2-[β-(2-furyl)vinyl]benzoxazole

Condensation of 2-methylbenzoxazole with 2-furfurylideneaniline in DMF afforded trans-2-[β-(2-furyl)vinyl]benzoxazole that was involved in the electrophilic substitution reactions (nitration, bromination, formylation, acylation) to give 5-nitro (bromo, formyl, acyl) derivatives. At the bromination in dichloroethane a hydrogen atom in vinyl group also underwent the substitution.

Synthesis and properties of trans-2-[2-(2-hetaryl)vinyl]benzothiazoles

Electrophilic substitution reactions (formylation and acylation) in the series of 2-[2-(2-furyl)vinyl]- and 2-[2-(2-thienyl)vinyl]benzothiazoles leads to the corresponding derivatives at the α-position of the furan or thiophene ring. The presence of a vinylene bridge weakens deshielding effect of the benzothiazole fragment on π-excessive heterocycles, so that such compounds react at a higher rate and under milder conditions as compared to hetarylbenzothiazoles having no vinylene bridge.

2-(2-Furyl)-5,6-dihydro-1(3)H-acenaphtho[4,5-d]imidazole. Synthesis and electrophilic substitution reactions

Abstract2-(2-Furyl)-5,6-dihydro-1(3)H-acenaphtho[4,5-d]imidazole was synthesized by the Weidenhagen reaction of acenaphthene-4,5-diamine with furfural. Alkylation of the title compound with methyl iodide in KOH-DMSO gave isomeric 1- and 3-methyl derivative, the latter being the major product. 2-(2-Furyl)-3-methyl-5,6-dihydro-3H-acenaphtho[4,5-d]imidazole was subjected to electrophilic substitution reactions (bromination, nitration, formylation, acylation, and sulfonation. Depending on the conditions, electrophilic attack was directed at the furan ring or acenaphthene fragment or both these.

Synthesis and some transformations of 2-(2-furyl)naphtho[1,2-d]oxazole

By condensation of 1-amino-2-hydroxynaphthalene with furoyl chloride in 1-methyl-2-pyrrolidone 2-(2-furyl)naphtho[1,2-d]oxazole was synthesized and brought into electrophylic substitution reactions: nitration, bromination, sulfonation, formylation, and acylation. The substituent commonly was introduced into the position 5 of the furan ring, but at the nitration and bromination electrophilic attack was directed both at the furan ring and the naphthalene fragment.