A. V. Koblik

Synthesis and properties of 3-formyl-4H-pyrans

The Vilsmeier formylation of 4H-pyrans afforded 3-formyl-4H-pyrans. These were converted to 3-formylpyrylium salts, from which pyridine or pyridine salts with an aldehyde group at C(3) were obtained. The reaction between 3-formyl-4-allyl-4H-pyran and methyltrifluoromethanesulfonate proceeded via a Koop rearrangement.

Synthesis of 6-hetaryl-substituted azulenes and their reactions with 2,6-diphenylpyrylium perchlorate

A method for the synthesis of 4,6,8-trimethyl- and 4,8-dimethyl-6-(2-thienyl, 2-benzothiazolyl) azulenes from 2,6-dimethyl-4-(methyl, 2-thienyl, 2-benzothiazolyl)-pyrylium perchlorates and cyclopentadienyllithium is described. The possibility of direct pyrylation of azulenes with 2,6-diphenylpyrylium perchlorate is demonstrated. Azulenes with a pyrylium ring in the 1 position were synthesized, and their behavior with respect to ammonium acetate was investigated.

Organosodium compounds of N-substituted benzimidazoles

The corresponding 2-sodioimidazoles were obtained from N-substituted imidazoles and phenylsodium. If the 2 position of imidazole is occupied, the 5-sodio derivative is formed.

Ethynyl carbonium ions. 3. Diene synthesis with 4-phenylethynylpyrylium salts

Norbornadiene derivatives of pyrylium salts were obtained for the first time by [4+2] cycloaddition of cyclopentadienes and 2,6-diaryl-4-phenylethynylpyrylium salts with and without methyl groups in the 3 and 5 positions. Their photochemical transformations were studied.

Ethynyl carbonium ions. 2. Reactions of 4-ethynylpyrylium perchlorates with alcohols and nitrogen-containing nucleophiles

Derivatives of Β-alkoxy- and Β-(phenylamino)styrylpyrylium salts, the hydrolysis of which leads to phenacylpyrylium salts and 4-benzoylmethylenepyrans, are formed in the reaction of 4-phenylethynylpyrylium salts with alcohols and aromatic amines. Ethynyl-substituted pyridines and pyridinium salts were synthesized by the action of ammonium acetate and methylamine, benzylamine, and butylamine. A Β-methylaminostyryl-1-methyl-substituted pyridinium salt is formed with excess methylamine.

Acylation of 2,4-diaryl-4H-chromenes by the action of acetic anhydride and perchloric acid

Abstract4H-Chromenes were found to be acylated at the 3-position by the action of acetic anhydride and perchloric acid. The structure was determined of other reaction products — the indenobenzopyrylium and 2,4-diaryl-1-benzopyrylium salts.

Regioselectivity of reduction of 2-tert-butyl-1-benzopyrilium perchlorate

The reaction of 2-tert-butyl-1-benzopyrilium perchlorate with various reducing agents leads to a mixture of 2H- and 4H-chromenes. The greatest selectivity (90% 2-tert-butyl-4H-chromene and 10% 2H-isomer) was achieved using 1,3-dimethylbenzimidazoline.

Ethynyl carbonium ions. 1. Reaction of 2.6-diaryl-4-phenylethynylpyrulium perchlorates with oxygen-containing nucleophiles

When 2,6-diaryl-4-phenylethynylpyrylium perchlorates are refluxed in water, methanol, or ethanol, they are converted to monomethinecyanines, the formation of which is explained by hydration of the phenylethynyl group and subsequent [2+2]-cycloaddition of the resulting 2,6-diaryl-4-benzoylmethylenepyrans to the starting pyrylium salt. The corresponding pyridine derivatives were obtained by the action of ammonia and aniline on the monomethinecyanines. The IR and PMR spectra of the compounds and the results of x-ray diffraction analysis of 2,6-diphenyl-4-[1′-(2″,6″-diphenyl-4″-pyranylidene)-2′-phenyl-3′-benzoylallyl]pyridine are presented.

Synthesis of 1-benzoxepines from dichlorocarbene adducts of chromenes

Synthesis of 1-benzoxepines by dehydrochlorination of carbene adducts of chromenes has been carried out. Different alkyl-, alkylidene-, alkoxy-, aryl- and hetarylsubstituted 1-benzoxepines were obtained.

Synthesis of hetaryl-substituted pyrylium salts and hetarylpyridines from tertiary heterocyclic carbinols

The synthesis of dimethyl benzothiazol-2-yl, 2-thienyl, and 1-methylbenzimidazol-2-yl carbinols and their acylation with acetic anhydride in the presence of perchloric acid have been performed. A method for the synthesis of 4-(benzothiazoI-2-yl)-2,6-dimethylpyrylium and 4-(2-thienyl)-2,6-dimethylpyrylium perchlorates has been developed; these substances are converted by treatment with aqueous ammonia, into the corresponding 4-(2-hetaryl)-2,6-di-methylpyridines.