Vladimir T. Abaev

A Simple Route to Polysubstituted Indoles Exploiting Azide Induced Furan Ring Opening

A straightforward, efficient indole synthesis based on thermolysis of 2-(2-azidobenzyl)furans with attack of the formed nitrene moiety onto the ipso position of furan ring has been developed. The cyclization is accompanied by furan ring opening and affords indoles with a 2-acylvinyl substituent suitable for further modifications.

o-Nitroaryl-bis(5-methylfur-2-yl)methanes as Versatile Synthons for the Synthesis of Nitrogen-Containing Heterocycles

2-Nitroaryldifurylmethanes 1a and 1b, readily available by condensation of 2-nitrobenzaldehyde and 6-nitroveratraldehyde with 2-methylfuran, were transformed into indole, cinnoline and benzothiazine-3,1 derivatives. The reduction of 2-nitroaryldifurylmethanes gave the corresponding anilines 2a,b or indole 3 depending on the reaction conditions. A plausible mechanism for the last reaction involving intramolecular heterocyclic addition between a nitroso-group and a furan ring is proposed. Diazotisation of the amine 2b gave a cinnoline derivative - a product of intramolecular oxidative furan ring opening. Treatment of isothiocyanates 7a,b with perchloric acid resulted in a new rearrangement with furan ring migration leading to the 4-Hbenzothiazine-3,1 derivatives.

Furyl(aryl)alkanes and Their Derivatives. 19*. Synthesis of Benzofuran Derivatives via 2-Hydroxyaryl-R-(5-methylfur-2-yl)methanes. Reaction of Furan Ring Opening - Benzofuran Ring Closure Type

2-Hydroxyaryl(5-methylfur-2-yl)alkanes synthesized by alkylation of 2-methylfuran with various 2-hydroxybenzylic alcohols, were rearranged into corresponding 3-R-benzo[b]furan derivatives by treatment with ethanolic HCl solution. These compounds can not be transformed into dibenzoxazulenium salts.

Furyl(aryl)methanes and their Derivatives. Part 21: Cinnoline Derivatives from 2-Aminophenylbisfurylmethanes

Abstract (Z)-4-[4-(5-Methyl-2-furyl)-3-cinnolinyl]-3-buten-2-ones and (Z)-1-[4-(5-ethyl-2-furyl)-3-cinnolinyl]-1-penten-3-ones have been obtained from 2-aminoarylbisfurylmethanes under treatment with isoamyl nitrite/trimethylchlorosilane in dry acetonitrile. Intramolecular cyclisation and furan oxidative ring opening follow the formation of an intermediate diazonium salt. X-Ray analysis proved the cis-configuration of the alkene side chain.

Acid Catalyzed Reactions of Substituted Salicylaldehydes with 2-Methylfuran

Data, concerning condensation reactions of salicylaldehydes and 2-methylfuran are generalized. During the course of investigation a sequence of proceeding transformations is established. It is shown that it is possible to obtain 2-hydroxyarylbis(5-methylfur-2-yl)methane, benzofuran or oxazulene derivatives selectively by simple changing of the reaction conditions.

New Synthesis of 3-(2-Furyl)phthalides

Abstract3-(2-Furyl)phthalides were synthesized for the first time by the reaction of 2-formylbenzoic acids with furan derivatives in the presence of an acidic catalyst. It was found that the reaction of 2-formylbenzoic acids and 2-alkylfurans in aqueous dioxane in the presence of perchloric acid leads to a mixture of 2-carboxyaryldifurylmethanes and 3-furylphthalides, which can be separated easily by preparative column chromatography.

Polyfuryl(aryl)alkanes and their derivatives. 17. Synthesis of compounds of the oxazulene series

Preparative methods were developed for the synthesis of various compounds of the benzofurooxazulene series. It was established that the formation of an oxazulenium salt and a dihydrooxazulene derivative during the treatment of 3-(5-methyl-2-furyl)-2-(3-oxobutyl)benzofurans with perchloric acid results from disproportionation of the intermediate compound—an oxazulene derivative.

Simple and Convenient Synthesis of 4-Unsubstituted-3- (3-Oxoalkyl)isocoumarins

Abstract A simple transformation of 2‐alkylfurans and 2‐formylbenzoic acids into 4‐unsubstituted 3‐(3‐oxoalkyl)isocoumarins is described. It is based on the synthesis of 2‐(2‐carboxybenzyl)furans followed by their acid‐catalyzed recyclization to the target isocoumarins.

Polyfuryl(aryl)alkanes and their derivatives 16. Convenient path to benzofuran ketones

Abstract2-(3-Oxobutyl)-3-(5-methyl-2-furyl)benzofurans were synthesized by the recyclization of 2-hydroxyarylbis(5-methyl-2-furyl)methanes in methanol saturated with hydrogen chloride. They can also be obtained by the reaction of salicylaldehydes and sylvane in an ethanol solution of hydrogen chloride.

The Butin reaction

This review summarizes the reported data on the Butin reaction, i.e., acid-catalyzed transformations of furans to a range of other heterocycles via intramolecular attack of nucleophile, connected to the α-carbon atom of furan ring by three- to six-membered linker, on the same α-carbon atom.