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.     

Pyrans,their analogs,and related compounds

Reaction of 4, 4-dichloroflavine (I) with sulfurylchloride affords 2, 3, 3, 4, 4-pentachloroflavan (II). Hydrolysis of II gives 2-hydroxy-3, 3-dichloro-4-flavanone (III), while alcoholysis with aqueous alcohols yields 2-alkoxy-3,3-dichloro-4-flavanones (IVa, b). Treatment of III with SOCl₂ gives 2,3,3-trlchloro-4-flavanone (V), which with caustic alkali or sodium ethoxide is converted into o-(1-phenyl-2, 2-dichlorovinyloxy)benzoic acid (VIc) or its ethyl ester (VIb), respectively.For Part XLII, see [7].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1167–1170, September, 1970.     

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].     

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.     

New reactions, functional compounds, and materials in the series of coumarin and its analogs

Data on the development of new functional compounds and materials based on the study of the reactions of coumarin and its analogs are generalized. Since coumarin derivatives are characterized by enhanced photochemically activity, special attention is given to the synthesis of photosensitive compounds and materials with intense fluorescence, including the structures capable of changing fluorescence under the action of various factors: solvent, pH of the medium, and interaction with bioorganic substrates. Pathways for design of fluorescent polymethine dyes, fluorescent labels for proteins, fluorescent photochromes, and photoacids for optical data storage with fluorescence read-out are reviewed. The role of isomerization transformations of the new compounds in their sensorial effects is established.     

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).     

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.     

Synthesis, structures and optical properties of trisilasumanene and its related compounds

Novel trisilasumanenes that have no substituents on the exo carbon atoms, silicon analogues of sumanene, were prepared via repetitive lithiations of triphenylene followed by introduction of silicon functionalities. The optical properties of these trisilasumanenes and their related compounds were investigated by UV-vis and fluorescence spectroscopy.     

99mTc-labeling of mercaptoacetyltriglycine and its related compounds

Mercaptoacetyltriglycine and its related compounds were synthesized and labeled with^99mTc-radionuclide in order to study the effect of substituents and labeling conditions upon the formation of radioactive by-products. Direct labeling and ligand exchange reactions were followed by radio-TLC separation. The direct labeling in alkaline media at elevated temperature provides high radiochemical yields and gives opportunity for a new kit formulation because the neutralization to physiological pH does not cause any change in the chemical identity of the complexes. Compounds with the strongly polar sulfonyl groups show significantly lower protein binding compared with mercaptoacetyltriglycine and may be considered as potential renal agents.     

Reaction of perfluorodimethylm ercury and its analogs with silyl- and stannylmercury compounds

Conclusions Bis(triethylsilyl)mercury reacts with HgR₂(R=CF₃, CF₂CF₃) to give the corresponding perfluoro-alkyl(triethylsilyl)mercury compounds. The analogous reaction with bis [tris(trimethylsilylmethyl) stannyl]-mercury is catalyzed by fluoride anions and is complicated by the decomposition of the unsymmetrical stannylmercury compounds.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 189–191, January, 1973.     

Carbon-13 NMR spectra of DDT,its analogues and related compounds

Carbon-13 NMR spectra of mono- and disubstituted aromatic compounds including DDT, its analogues, homologues, derivatives and certain model compounds have been studied. The Savitsky scheme of carbon chemical shifts in disubstituted benzenes is applicable to these compounds. The data obtained show that in mono- and disubstituted aromatic compounds containing two different substituents in the α- and β-positions of the side chain, the substituted ring carbon atom shifts follow the additivity rule and can be calculated from substituent increments. Mutual effects of substituents in the ring and in the side chains are analysed. The chlorine atoms in α-position to the phenyl ring give rise to an additive α-effect of about 25 ppm, as in perchloroalkanes. The influence of a β-chlorine atom in the side chain on the substituted carbon atom in the ring is, however, only 3 ppm as against the usual value of about 10 ppm for the β-effect in alkyl chains. Moreover, the first β-chlorine substituent has no noticeable influence on the substituted ring carbon chemical shift: the effect of 3 ppm is transferred to the para-carbon atom almost without attenuation. The ring substituted carbon atom signal shifts caused by the γ-effect of chlorine in the side chain are similar to those observed in aliphatic chains. The ortho-chlorine substituents shift the side chain α-carbon atom signal by 3.6-5.2 ppm to high field compared to para-chlorophenyl compounds. This is similar to the chlorine γ-effect in aliphatic chains.     

Acid dissociation of 2-mercaptohistamine and its related compounds

The acid dissociation constants of 2-mercaptohistamine hydrochloride (2-MH) and its related compounds ergothioneine (Erg), 2-mercaptoimidazole (MI), N-methyl-2-mercaptoimidazole (MMI) and histamine dihydrochloride were determined by potentiometry at 15 degrees , 25 degrees and 35 degrees and mu = 0.1 (NaClO(4)). The values of DeltaH and DeltaS for the ionization equilibria were calculated. The magnitude of DeltaH (9.5 kcal/mole) for pk(a1) of 2-MH is similar to the value DeltaH = 9-10 kcal/mole found for the ionization of a number of amino groups. The value DeltaH = 7.4 kcal/mole for pk(a2) of 2-MH is similar to the values for the ionization of a variety of thiols (DeltaH = 5-7 kcal/mole). Such values were not obtained for Erg, MI and MMI, which suggests that 2-MH exists mainly in the thiol form, whereas Erg, MI and MMI are in the thione form.     

Complete NMR assignment of retinal and its related compounds

Complete and unambiguous ¹H and ¹³C NMR chemical shift assignments for all‐trans‐retinal, 13‐cis‐retinal, 11‐cis‐retinal and 9‐cis‐retinal (1–4) have been established by means of two‐dimensional COSY, HSQC, HMBC and NOESY spectroscopic experiments. Copyright © 2013 John Wiley & Sons, Ltd.