Side products in the rosenmund reduction of benzofuran-2-carboxylic acid chlorides

The corresponding 1,2-bis(2-benzofuryl)ethylenes and 2-methylbenzofurans were isolated as side products, along with the principal reaction products (2-formylbenzo-furans), in the Rosenmund reduction of 3-, 5-, and 7-alkylbenzofuran-2-carboxylic acid chlorides. The bis(2-benzofuryl)ethylene structure was confirmed by the IR and PMR spectra data and alternative synthesis by reduction of the corresponding benzofuroins, obtained by benzoin condensation of 2-formylbenzofurans, with zinc amalgam in acidic media. The side formation of desoxybenzofuroin derivatives was noted in some cases in the benzoin condensation.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 744–748, June, 1977.     

The synthesis of 2-methylchromone-3-carboxylic acid

A new synthesis of 2-methyl-4-oxo-4H-1-benzopyran-3-carboxylic acid (2-methylchromone-3-carboxylic acid from salicyloyl chloride and the enamine of ethyl acetoacetate, is described and compared with the classical synthesis.     

Azetidine-2-carboxylic acid derivatives

An improved method for the preparation of DL -azetidine-2-carboxylic acid is reported. The reaction of thionyl chloride with azetidine-2-carboxylic acid in methanol gave rise to 2-carbomethoxyazetidine hydrochloride, which upon treatment with triethylamine yielded 2-carbomethoxyazetidine. 2-Carbomethoxyazetidine proved to be unstable and upon standing formed azetidine-2-carboxylic acid anhydride. The nmr and ir spectra of 2-carbomethoxyazetidine are discussed in terms of its conformation. The conversion of azetidine-2-carboxylic acid to azetidine-2-carboxamide is also described.     

Derivatives of l-H-aziridine-2-carboxylic acid

The reaction of 1,1-dimethylhydrazine with acrylic acid derivatives gave a number of 1,1-dimethyl-2-(2-substituted ethyl)hydrazines, which were quaternized by alkylating agents. The transformations of 1,1,1-trimethyl-2-(2-substituted ethyl)hydrazinium salts in the presence of sodium methoxide were investigated. 2-Cyano-, 2-carbomethoxy-, 2-carbethoxy-, and 2-carbodiethylamidoaziridines and a number of products of decomposition of the starting salts were obtained.     

The birch reduction of heterocyclic compounds. III. Birch reduction-elimination reaction of 2- and 3-furancarboxylic acid derivatives

The Birch reduction of 2-(1-alkoxyalkyl)furan-3-carboxylic acids 1a-f gave 2-alkyl-3-furancarboxylic acids 2a-f with loss of the alkoxyl group in excellent isolated yields.     

Chlorination of tetrahydrofuran-2-carboxylic acid esters

The photochemical chlorinatlon of tetrahydrofuran-2-carboxylic acid esters with chlorine at –15 to –20C leads primarily to the formation of 5-chlorotetrahydrofuran-2-carboxylic acid esters (70–80%). 4,5-Dihydrofuran-2-carboxylic acid and furan-2- carboxylic acid esters are formed as side products. The structures of the principal and side products were investigated by PMR and mass spectroscopy.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 166–168, February, 1979.     

Synthesis of 5-nitrofuran-2-carboxylic acid

5-Nitrofuran-2-carboxylic acid was obtained in quantitative yield by oxidation of 5-nitrofurfural with hydrogen peroxide and decomposition of the intermediate 5-nitrofurfural α-hydroxyhydroperoxide. The mechanism of the reaction is discussed.     

Polarography of furan-2-carboxylic acid esters

The polarographic reduction of furan-2-carboxylic acid esters in dimethylformamide was studied. The E_1/2 values correlate with the * constants for the substituents in the alcohol part of the 2-furoates.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 890–892, July, 1982.     

Synthesis and conversions of piperazine-2-carboxylic acid

A method has been developed for the synthesis of methyl piperazinium-2-carboxylate dihydrochloride (overall yield 46%) and piperazinium-2-carboxylic acid dihydrochloride (overall yield 36%), from ethylene diamine through N,N-di(trifluoroacetyl) ethylenediamine and methyl N,N-di(trifluoroacetyl)piperazine-2-carboxylate. The N,N-dinitroso derivatives were synthesized.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 833–836, June, 1985.     

Enamino derivatives of 1,3-dioxoindane-2-carboxylic acid

Although 1,3-dioxoindane-2-carboxylic acid is highly unstable, its enamino derivatives can be isolated by careful hydrolysis of their esters with 2,4-dihydroxy-1,4-naphthoquinone. Crystal structure determination reveals the formation of two intramolecular hydrogen bonds, offering thus a possible explanation for the stability of these acids.     

Practical asymmetric preparation of azetidine-2-carboxylic acid

[reaction: see text] Facile and straightforward syntheses of both enantiomers of azetidine-2-carboxylic acid are described. The syntheses depart from inexpensive chemicals and allow for the production, in five to six steps, of practical quantities of each enantiomer. Synthetic highlights include the construction of the azetidine ring using an intramolecular alkylation and the use of optically active alpha-methylbenzylamine as chiral auxiliary.     

Enantiodivergent synthesis of N-protected azetidine-2-carboxylic acid

A new route to both enantiomers of N-tosyl-azetidine-2- carboxylic acid has been developed from (R)-2-cyclohexylideneglyceraldehyde which proceeded with good overall yield and excellent enantiomeric purity.     

Phenazines—V The synthesis of 2-aminophenazine-1-carboxylic acid

2-Aminophenazine-1-carboxylic acid has been obtained from the ester which resulted from the oxidative cyclization in boiling nitrobenzene of the methyl esters of both 2,4-diaminodiphenylamine-3- and 2′,3-diaminodiphenylamine-2-carboxylic acids. The acid was also prepared via the very unreactive nitrile, the latter being obtained from 2-amino-1-bromophenazine which was produced by the direct bromination of 2-aminophenazine.     

Synthesis of 4-imidazolin-2-ones via the birch reduction of hydantoins

The reduction of 5-(5-methyl-2-furyl)hydantoin to 4-(5-methyl-2-luryl)-4-imidazolin-2-one is described.     

Synthesis of new 3,3-dimethoxyazetidine-2-carboxylic acid derivatives

Cyclization of γ-amino-α-bromocarboxylic esters resulted in an efficient synthesis of new 3,3-dimethoxyazetidine-2-carboxylates, that is, methyl N-t-butyl-3,3-dimethoxyazetidine-2-carboxylic ester and 3,3-dimethoxyazetidine-2-carboxylic acid, or 3-bromo-4,4-dimethoxypyrrolidin-2-ones, depending on the substituent at nitrogen. Reduction of the 3,3-dimethoxyazetidine-2-carboxylates gave the corresponding 3,3-dimethoxy-2-(hydroxymethyl)azetidines. These novel cyclic amino acid derivatives, available on multigram scale, have a suitably protected carbonyl function at the 3-position, which enables further functionalization.     

A convenient synthesis of 5-fluorofuran-2-carboxylic acid

A convenient synthesis of 5-fluorofuran-2-carboxylic acid has been achieved in two steps and 56% total yield. Fluorodenitration of commercially available benzyl 5-nitrofuran-2-carboxylate utilizing potassium fluoride and catalytic tetraphenylphosphonium bromide in sulfolane at 140 °C for 2 h furnished benzyl 5-fluorofuran-2-carboxylate. Hydrogenolysis of benzyl 5-fluorofuran-2-carboxylate gave the title compound.