Research on pyranes,their analogs,and related compounds

By the reaction of 2- acylaminochromones with formaldehyde and secondary amines, we have synthesized 2-acylamino-3-dialkylamino-methylchromones. On the basis of their chemical properties and their UV, IR, and NMR spectra, a hypothesis concerning the fine structure of these compounds has been put forward. When the reaction with formaldehyde is carried out in the presence of bases, 3, 3'-methylenebis-(2-acylaminochromone)s can be obtained.For part XXVI, see [3].     

Research on pyranes,their analogs,and related compounds

The action of methanol on methyl 4, 4-dichlorochromene-2-carboxylate (A) gives a 2-substitution product I, readily hydrolyzed in acid solution to a 2-hydroxy derivative C, which undergoes an allylic rearrangement to an ester of chromane-2-carboxylic acid B. Hydrogenation of compound I gives 2-methoxy-2-carbomethoxychromane (II), which is caused to undergo some chemical reactions.For Part XXIII see [4]     

Researches on pyranes,their analogs,and related compounds

Condensation of 2, 4-diacetylphenol with diethyl oxalate serves as a basis for preparing 2-carbethoxy- and 2-carboxy-6-acetylchromones (I, II), 2-carbethoxy-6-ethoxyoxalyacetylchromone (V), and 2-carboxy-6-hydroxyoxalylacetylchromone (VI). The Mannich reaction is used to synthesize 6-(ω-dialkylaminopropionyl)-2-carboxychromones (VII, VIII) from compound I. Reaction of chromone-2-carbonyl chloride with enamines prepared from cyclohexanone and tetrahydrothiopyrone-4- gives syntheses of 2-(chromonoyl-2)cyclohexanone (III) and 3-(chromonoyl-2)tetrahydrothiopyrone-4 (IV). Hydrazine hydrate and compound III give the pyrazole derivative IX, while hydrazine hydrate and compound IV give pyrazole derivative X along with pyrazolylpyrazole derivative XI, which results from a second molecule of hydrazine hydrate opening the chromone ring. For Part XX see [11].     

Pyran,its analogs,and related compounds

The effect of amines (benzylamine, N,N-dimethylethylenediamine, and ethylenediamine) on the tert-butyl ester (I) and tert-butyl amide (II) of chromone-2-carboxylic acid was studied. In contrast to the sterically unhindered derivatives of chromone-2-carboxylic acid, I and II do not undergo amidation or transamidation by reaction with the amines but are converted directly to pyran-ring-opening products. In the case of ethylenediamine, further intramolecular cyclization also occurs to form 5-(o-hydroxyphenyl)-7-carboxy-1,4-diaza-4,6-cycloheptadiene derivatives (VII and IX).See [6] for communication XXXVIII.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 17–21, January, 1971.     

Studies on pyran,its analogs,and related compounds

The action of guanidine on esters of chromone-2-carboxylic acids leads to the opening of the pyrone ring and to the formation of hydantoin derivatives — 2-imino-5-(2-hydroxybenzoylmethylene)tetrahydroimidazol-4-ones — in addition to other reaction products.Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 6, No. 7, pp. 874–875, July, 1970.     

Studies in pyran,its analogs,and related compounds

The lithium aluminum hydride reduction of the ethers and tosylates of chroman-4-one oxime and related compounds has been studied. It has been found that the ethers of the oximes, like the oximes, do not undergo a normal, but rather an anomalous, reduction. The tosylates of the oximes exhibit a higher tendency to undergo anomalous reduction than the corresponding oximes. During the synthesis of the ethers of the oximes it was established that the use of dimethylformamide as the medium for alkylation of the oxime salts helps to suppress the side reaction forming nitrones.For part XXXVII, see [23].     

Studies on pyran,its analogs,and related compounds

The bromination of 6,7-dibenzyloxy-4-methylcoumarin has given 6,7-dibenzyloxy-3-bromo-4-methylcoumarin and this has been converted by the Perkin reaction into 5, 6-dibenzyloxy-3-methylbenzofuran and its 2-carboxy derivative. 5, 6-Dihydroxy-3-methylbenzofuran-2-carboxylic acid has been synthesized by the catalytic debenzylation of the latter compound.For part XXV, see [12].     

Studies on pyran,its analogs,and related compounds

The bromination of 6,7-dibenzyloxy-4-methylcoumarin has given 6,7-dibenzyloxy-3-bromo-4-methylcoumarin and this has been converted by the Perkin reaction into 5, 6-dibenzyloxy-3-methylbenzofuran and its 2-carboxy derivative. 5, 6-Dihydroxy-3-methylbenzofuran-2-carboxylic acid has been synthesized by the catalytic debenzylation of the latter compound.     

Research into analogs of pyran and related compounds

The reaction of esters of 4, 4-dichlorochromene-2-carboxylic acid and of 4, 4-dichloroflavine (4, 4-dichloro-2-phenyl-4H-l-benzopyran) with compounds containing an activated methyl group (cyanoacetic ester, cyanoacetamide, and malonodinitrile) is examined. These dichloro compounds undergo substitution in both the 2-and 4-positions of the chromene system, depending on the nature of the attacking reagent. The initially formed esters of 2-ethoxycarbonylcyanomethyl-4-chloro-3-chromene-2-carboxylicacid undergo a number of specific reactions, since the cyanoacetate group attached to the chromene system is sufficiently labile to be capable of removal of hydrolysis, and of migration to the 4-position.For part XXVIII, see [9].Preliminary part, ZhOKh, 34, 1685, 1964.     

Reissert compounds and their open-chain analogs in organic synthesis

Reactions of major synthetic interest employing Reissert compounds (1, 2-dihydro-1-acyl-2-cyanoquinolines and 1, 2-dihydro-2-aqyl-1-cyanoisoquinolines) and related heterocyclic species are surveyed. The chemistry of open-chain analogs of Reissert compounds (i.e., derivatives of N-acyl-α-aminoacetonitriles) is described and compared with conventional Reissert compounds.     

Meldrum's acid and related compounds in the synthesis of natural products and analogs

This critical review focuses on applications of Meldrum's acid and its derivatives to the synthesis of natural products and analogs. It covers all relevant literature from 1991 to August 2007 (181 references).     

Separation of organic compounds and their deuterated analogs by preparative gas chromatography

Conclusions Using the circulation GLC method we were able to effect the preparative separation of some ordinary and fully deuterated products with an efficiency that is comparable to that achieved using capillary chromatography and exceeds 40 thousand theoretical plates.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimieheskaya, No. 7, pp. 1627–1629, July, 1977.     

Studies on pyrrolidinone. Synthesis of aza analogs of podophyllotoxin and related compounds

The Friedel-Crafts cyclisation of N-benzhydrylpyroglutamic acids whose aromatic rings are substituted by methoxy or methylenedioxy groups gives podophyllotoxin analogs whose lactone ring was changed to a lactam.     

Thin-layer chromatography of some organic selenium compounds and their oxygen and sulfur analogs

The Chromatographic behavior of some series of organic selenium compounds and their oxygen and sulfur analogs (urea, thiourea, selenourea; xanthene, thioxanthene, selenoxanthene; xanthone, thioxanthone, selenoxanthone) has been examined by thin-layer chromatography (TLC) on silica gel. The experimental results show the possibility of attaining fast separations on very small amounts of substance (at the microgram level) by simple monodimensional TLC techniques. Urea and its S and Se analogs as well as xanthones are well separated by two- or three-component eluting solvents; xanthenes are not easily screened even by solvent mixtures. The separation of xanthenes from xanthones by the two-dimensional TLC technique is also described. A further result is the possibility of detecting species in trace amounts in the matrix being examined.     

Cyclazines and their analogs

The formylation of 2-methyl-6-cyanomethylthiopyridines, 2-methyl-4-cyanomethylthiopyrimidines, or 3-amino-5-methylthiazolopyrimidinium salts gave cyclazine derivatives of new heterocyclic systems with an angular nitrogen atom, which were used for the preparation of polymethine dyes. The relationship of the color and structure of these compounds was studied.For Communication 2, see ref. [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1280–1285, September, 1992.     

Cyclazines and their analogs

Derivatives of a new heterocyclic system, formyl-substituted thiazolopyrimidopyrimidines, are synthesized through reaction of 3-amino-5-methyl-thiazolo[3,2-a]pyrimidinium salts, prepared by alkylation of 2-mercaptopyrimidines with substituted acetonitriies, and the Vilsmeier reagent. These can be used to synthesize polymethine dyes.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 692–697, May, 1992.     

Azolidine-4-thiones,their derivatives and analogs

The reaction of rhodanine with P₂S₅ in various solvents was investigated with a view to converting the CO group to CS. Using dry dioxane, a 90% yield of the hitherto unknown thiazolidine-2, 4-dithione (thiorhodanine I) was obtained, distinguished by having a quite active methylene group, which readily coupled with diazonium salts in neutral solutions, as well as condensing with aldehydes in methanol. It was very readily oxidized. Its 4-thione group condensed with amines. A qualitative test for I was reaction with p-dimethylaminobenzaldehyde to give an intense red color. 5-Arylidene-5-arylazo and 4-arylimino derivatives of I have been isolated.     

Azolidine-4-thiones,their derivatives and analogs

4-Thioxothiazolid-2-one (isorhodanine) is distinguished from the initial thiazolidine-2,4-dione, and also from rhodanine and other azolid-4-ones, by the highly active C=S group in position 4. When isorhodanine is heated in methanol with various amino compounds, condensation products-substituted 4-iminothiazolid-2-ones-are obtained.For part V, see [10].