Cyclization of N-diacetic amino acids

Cyclization of a number of N-diacetic amino acids has been carried out. The dependence of the cyclization products — 3,5-dioxopiperazinoalkanecarboxylic acids and/or their amides—on the temperature, ratio of components, and the presence of solvent has been established. Institute of Biochemistry of the Lithuanian Republic, Vilnius 2600. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1392–1396, October, 1998.     

Cyclization of acetylenic derivatives of aromatic carboxylic acids

The Cu(I)-catalyzed intramolecular cyclization of 1-phenylethynyl-and 1-hexyn-1-yl-anthraquinone-2-carboxylic acid is a 6-endo-dig-addition, whereas the reaction for 1-(3-phenoxypropyn-1-yl)anthraquinone-2-carboxylic acid proceeds in a directionally nonspecific way. It is shown that the cyclization of vicinal acetylenic derivatives of aromatic carboxylic acids leads to the formation of the more stable of the possible cyclic structures.Institute of Chemical Kinetics and Combustion, Siberian Branch, Russian Academy of Sciences, 630090 Novosibirsk. Novosibirsk State University, 630090 Novosibirsk. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 9, pp. 2138–2146, September, 1992.     

Cyclization of 4-ureidobutanoic acids in acetic anhydride

A simple method is proposed for synthesizing 1-carbamoyl-2-pyrrolidones by cyclization of 4-ureidobutanoic acids in acetic anhydride.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 33–38, January, 1995.     

Study of the heterocyclization of vic‐substituted hydrazides of acetylenylpyrazolecarboxylic acids into N‐amino pyrazolopyridinones

We report a new and efficient methodology to prepare N‐amino pyrazolo[4,3‐c]pyridin‐4‐ones 4 and N‐amino pyrazolo[3,4‐c]pyridin‐4‐ones 8 from vic‐acetylenyl/hydrazido pyrazoles. The procedure involves the intermediate synthesis of methyl esters of acetylenyl‐pyrazole carboxylic acids and the subsequent cyclization under a variety of conditions.     

Cyclization of o-acylphenylacetic acids to 1-aryl-3-hydroxyisoquinolines

Methyl o-acylphenylacetates react with urea to give 1-aryl-3-hydroxyisoquinolines. 1-Phenyl-2-methyl-3-isoquinolone was obtained by the action of methylamine on methyl o-benzoylphenylacetate. The lactim-lactam tautomerism of 1-aryl-3-hydroxyisoquinolines is discussed on the basis of their UV and IR spectra. The biological activity of some 1-aryl-3-hydroxyisoquinolines with respect to 16 strains of bacteria was studied.     

Cyclization of arylthiohydrazides of carboxylic acids under the influence of phosphorus halides

It is shown that arylthiohydrazides of carboxylic acids undergo cyclization to give both bis (1-methyl-2-indolyl) disulfides and salts of the corresponding 1-methyl-2-aminoindole under the influence of phosphorus halides (POCl₃ or PCl₃).Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 344–347, March, 1979.     

Cyclization of N-(4-quinazolyl)-α-amino carboxylic acids

2,3-Dihydroimidazo[1,2-c]quinazolin-2-one derivatives were obtained by cyclization of N-(4-quinazolyl)--amino carboxylic acids. A scheme including cleavage of the C(₂)-N(₃) bond of the quinazoline ring and subsequent rearrangement is proposed for the mechanism of the cyclization. The structures of the synthesized compounds were established by means of chemical and physicochemical methods.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1268–1271, September, 1976.     

Cyclization of 2- and 3-indolythioalkanoic acids to novel indole-containing tricyclic ring systems

A series of 2- and 3-indolylthioalkanoic acids of various chain lengths were cyclized under dehydrative conditions affording tricyclic indole-containing ring systems wherein the third ring contains a sulfur atom attached to the 2- or 3-position of the indole ring. This methodology affords entry into the novel thiepino[3,2-b]indole, thiocino[2,3-b]indole and thiocino[3,2-b]indole ring systems.     

Cyclization ofα- andβ-(arylseleno)alkylcarboxylic acids and their derivatives

The cyclization of- and-(arylseleno)alkylcarboxylic acids in polyphosphoric acid was studied. It was found that-(arylseleno)alkylcarboxylic acids do not cyclize under those conditions in which cyclization of the analogous-(arylseleno)alkylcarboxylic acids does occur. A convenient method for the preparation of 2-methylselenonapthanone by the cyclization of-phenylselenopropionyl chloride is proposed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 333–334, March, 1971.     

Cyclization of alkynoic acids with gold catalysts: a surprising dichotomy between Au and Au

ω-Acetylenic acids, substituted or not at their acetylenic end, could be efficiently cyclized to γ- or δ-alkylidene lactones in the presence of AuCl and K₂CO₃. In contrast AuCl₃ led to lactone dimers, probably through cyclization and reductive dimerization. These Au^I and Au^III catalyzed cyclizations were totally regioselective and most often highly stereoselective.     

A novel route to 5-substituted 3-isoxazolols. Cyclization of N, O-DiBoc beta-keto hydroxamic acids synthesized via acyl Meldrum's acids

3-Isoxazolols are most often synthesized from a beta-keto ester and hydroxylamine. This cyclization typically gives rise to a major byproduct, the corresponding 5-isoxazolone. We have found that N, O-diBoc-protected beta-keto hydroxamic acids can be synthesized and cyclized to 5-substituted 3-isoxazolols without formation of any byproduct. We present a novel and versatile three-step procedure in which carboxylic acid derivatives are converted into acyl Meldrum's acids which, upon aminolysis with N, O-bis(tert-butoxycarbonyl)hydroxylamine, lead to the N, O-diBoc-protected beta-keto hydroxamic acids. These hydroxamic acid analogues were then, upon treatment with hydrochloric acid, cyclized to the corresponding 5-substituted 3-isoxazolols.