Interactions of aroyl-and heteroaroyltrifluoroacetones with thiobenzoylhydrazine

The interaction of aroyl(heteroaroyl)trifluoroacetones with thiobenzoylhydrazine may occur at both carbonyl groups. Reaction at the trifluoroacetyl group is facilitated by terminal substituents in the 1,3-dicarbonyl part, which leads can effectively conjugate with the adjacent carbonyl group. The products of condensation at the trifluoroacetyl group are 2-[2-aryl(heteroaroyl)-2-oxoethyl]-5-phenyl-2-trifluoromethyl-2,3-dihydro-1,3,4-thiadiazoles, while condensation at the aroyl(heteroaroyl)group gave 3-aryl(heteroaryl)-5-hydroxy-1-thiobenzoyl-5-trifluoromethyl-4,5-dihydro-1H-pyrazoles, which are not prone to tautomeric transformations in solution. In Memory of Professor A. A. Potekhin __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 765–775, May, 2008.     

Substituent effects in the ring‐chain tautomerism of 4‐alkyl‐2‐aryl substituted oxazolidines and tetrahydro‐1,3‐oxazines

The condensation products of 2‐aminoethanol or 3‐aminopropanol (bearing an alkyl substituent on the carbon adjacent to the nitrogen) with substituted benzaldehydes proved to exist in CDCl₃ at 300 K as threecomponent tautomeric mixtures of the diastereomeric five‐ or six‐membered 1,3‐O,N‐heterocyclic ring forms and the corresponding imines. For each equilibrium, the electronic effects of the 2‐aryl substituents were characterized by the Hammett equation. The steric effects of the alkyl groups could be described by Hansch‐type equations for the equilibria involving oxazolidine ring forms. While the alkyl substituents did not cause any significant effect on the ring cis‐chain and the ring trans‐chain equilibria for tetrahydro‐1,3‐oxazines, increasing bulk of the 4‐alkyl group increased the stability of the cyclic tautomers for the analogous oxazolidines.     

Influence of intramolecular hydrogen bonds on the tautomeric equilibrium of 1,3-diketones

The paper deals with a quantitative characterization of the influence of multiple intramolecular hydrogen bonds on the tautomeric equilibrium of 1,3-diketones by means of NMR-spectroscopy. The contents of the keto- and two enol forms of 1-(o-hydroxyphenyl) -1,3-butandione and 1-(o-methoxyphenyl)-1,3-butandione in tetrachloromethane, deuterochloroforme, acetone-d₆ and acetonitrile-d₃ are compared.The intramolecular hydrogen bond between the phenolic hydroxyl group and the aromatic carbonyl group in 1-(o-hydroxyphenyl)-1,3-butandione shifts are keto-enol equilibrium toward the keto-tautomer and enol-enol equilibrium toward the tautomer with an enolized aliphatic carbonyl group.     

Synthesis of 2-aryl(hetaryl)-1-hydroxyimidazoles by the reaction of aliphatic 1,2-hydroxylamino oximes with aromatic and heteroaromatic aldehydes

A reaction of aliphatic 1,2-hydroxylamino oximes bearing the hydroxylamino group at the secondary carbon atom with aromatic and heteroaromatic aldehydes in acetic acid leads to the corresponding 1-hydroxy-2-aryl(hetaryl)-4,5-dialkylimidazoles in high yields. α-Aryl(hetaryl)-nitrones initially formed by the condensation of 1,2-hydroxylamino oximes with aldehydes are quantitatively converted to the corresponding imidazoles.     

Heterocyclic Derivatives of Fullerene C60. 1. Synthesis of New Fulleropyrazolines by the 1,3-Dipolar Cycloaddition of Nitrile Imines

New stable [6,6]-closed cycloadducts, fulleropyrazolines containing aryl, hetaryl, trifluoromethyl, and other substituents in the five-membered ring, have been obtained by the 1,3-dipolar cycloaddition of nitrile imines to C₆₀. Two methods of generating nitrile imines in situ have been used, the dehydrohalogenation of the corresponding hydrazonoyl halides by the action of triethylamine and the thermal decomposition of 2,5-diaryltetrazoles.     

N-(2-aminobenzoyl)-N-methylhydrazones of aldehydes and aldoses and their cyclization to benzo-1,3,4-triazepine derivatives

The products of the condensation of aliphatic aldehydes with N-(2-aminobenzoyl)-N-methylhydrazine exist in DMSO-d₆ solution as tautomeric mixtures of linear aldohydrazone and cyclic benzo-1,3,4-triazepine forms. The linear tautomer predominates for 2-aminobenzoyl-N-methylhydrazones of aromatic aldehydes. A tautomeric equilibrium is observed in DMSO-d₆ for the products of the condensation of the hydrazide of 2-aminobenzoic acid with a series of aldoses. This equilibrium exists between α,β-isomeric pyranose forms and the open aldosohydrazone form. Isomeric conversion to the seven-membered benzo-1,3,4-triazepine form is observed for the products of the condensation of aldoses with N-(2-aminobenzoyl)-N-methylhydrazine.     

New Multicomponent Synthesis of Functionalized Nitriles and Esters of 6-Alkylsulfanyl-1,4-dihydronicotinic Acids

The multicomponent condensation of malononitrile, hydrogen sulfide, aryl or hetaryl aldehydes, 1,3-dicarbonyl compounds and alkylating reagents afforded functionalized nitriles and esters of 6-alkylsulfanyl-1,4-dihydronicotinic acids, their aromatic analogues and 1,4-dihydrothieno[2,3-b]pyridines.     

Chemical Transformations of Tetracyclo[3.3.1.1<Superscript>3,7</Superscript>.0<Superscript>1,3</Superscript>]decane (1,3-Dehydroadamantane): VI. Reactions of 1,3-Dehydroadamantane with Carboxylic Acid Chlorides

1,3-Dehydroadamantane reacted with saturated carboxylic acid chlorides to give the corresponding 1-acyl-3-chloroadmantanes as the major products. In some cases, minor products of insertion into the C^α–H bond of acyl chloride were formed. The reactions of 1,3-dehydroadamantane with aromatic (heteroaromatic) carboxylic acid chlorides selectively afforded aryl (hetaryl) 3-chloroadamantan-1-yl ketones. The described reactions provide a synthetic route to difficultly accessible alkyl (aryl) ketones containing a 3-chloroadamantan- 1-yl group in one step under mild conditions with high yields.     

Ring - chain transformations with participation of the C = N group

The ring-chain tautomeric equilibrium constants (K) of aryl-ring-substituted 3-arylamino-3-phenylphthalides in dioxane were measured by UV spectroscopy. A satisfactory linear correlation between log K/K₀ and the σ⁺ constants of the substituents in the aryl ring was found.     

Synthesis of 2-(1-Alkoxyvinyl)oxazolidines by Condensation of 2-Alkoxypropenals with 2-Aminoalkanols and Ring-Chain Tautomerism of the Products

Reactions of 2-alkoxypropenals with 2-aminoalkanols afforded tautomeric mixtures of previously unknown 2-(1-alkoxyvinyl)oxazolidines and imino alcohols. The condensation takes 2 h at room temperature (89-100%) or 1-5 min under microwave irradiation. The tautomeric equilibrium shifts toward the open-chain structure with increase in the solvent polarity (CDCl₃, CD₂OD, DMSO-d ₆, D₂O) and temperature. The presence of substituents in the oxazolidine ring raises the stability of the cyclic tautomer.     

Heterocycles from aroylacetic aldehydes and SH-containing hydrazides

Condensation products of aroylacetic aldehydes with hydrazides of thioglycolic, 3-mercaptopropionic and 2-mercaptobenzoic acids exist in cyclic 1,3,4-thiadiazine, 1,3,4-thiadiazepine, or 1,3,4-benzothiadiazepine forms arising at the intramolecular addition of the mercapto group to the C=N bond of the initially formed hydrazone tautomer. The appearance of an alternative 5-hydroxy-2-pyrazoline form is favored by introduction of a strong electron-acceptor substituent into the aromatic ring of the 1,3-ketoaldehyde or by going over to benzoylacetone derivatives. In solutions the derivatives of aroylacetic aldehydes and of benzoylacetone show no tendency to tautomeric transition into linear hydrazine or enhydrazine forms.

     

Synthesis and antiphospholipase activity of 3,5-disubstituted thiotetronic acid derivatives

The condensation of 3-acetyltetrahydrothiophene-2,4-dione with aromatic aldehydes in the presence of piperidine as a catalyst gave a series of 5-arylmethylidene-3-acetyltetrahydrothiophene-2,4-diones. The reaction with excess aldehyde (2.5 equiv) led to the formation of bis-condensation products, 5-arylmethylidene-3-(3-aryl-1-oxoprop-2-enyl)tetrahydrothiophene-2,4-diones. Analogous 3,5-disubstituted tetrahydrothiophene-2,4-dione derivatives with different aryl groups in the ring and the side chain were synthesized by two-step condensation with the use of differently substituted aromatic aldehydes. Catalytic hydrogenation of both mono-and bis-adducts resulted in the reduction of the side-chain double C=C bond, while ionic hydrogenation with triethylsilane in trifluoroacetic acid in the presence of lithium perchlorate involved both the double C=C bond and carbonyl group in the side chain. The isolated products showed an appreciable effect on the activity of two secretory phospholipases A₂ from various sources.     

Tautomeric equilibria in the reaction products of asymmetric 1,3-diamines with β-dicarbonyl compounds

The reaction products of 1,3-butanediamine and 2-methyl-2,4-pentanediamine with β-keto aldehydes were shown by ¹H and ¹³C NMR spectroscopy to exist as tautomeric mixtures in solutions, comprising one cyclic and two open-chain forms due to the non-equivalence of the amino groups. The chain products exist as Z- and E-isomers. After equilibration, the products from 1,3-butanediamine contain relatively less of the cyclic form than those from 2-methyl-2,4-pentanediamine. The products of 2-methyl-2,4-pentanediamine with p-substituted aroylacetaldehydes, exhibit a linear correlation between log K of the ring-chain equilibria and Hammett's σ values of the aromatic ring substituents. α-Substitution of β-keto aldehydes notably increased the relative amounts of the chain E-isomers in their condensation products and also resulted in the formation of two diastereomers for each of the cyclic products. No ring-chain equilibria were observed in the products of 1,3-butanediamine and 2-methyl-2,4-pentanediamine with β-diketones, β-keto esters, or β-keto amides.     

Tautomerism and conformational isomerism of mercaptoacetylhydrazones of aliphatic and aromatic aldehydes

Mercaptoacetylhydrazones of aliphatic and aromatic aldehydes exist in the solutions as tautomeric mixtures of open-chain and cyclic 1,3,4-thiadiazine forms. The linear hydrazone form consists of a set of isomers due to the configurational and conformational isomerism. At growing bulk of the alkyl substituent at the C=N bond of the aliphatic aldehydes derivatives decreases the fraction of the cyclic tautomer; therewith the logarithms of the constants of the chain-ring tautomeric equilibrium correlate with the steric constants of the alkyl substituents. In the series of the aromatic aldehydes mercaptoacetylhydrazones the linear tautomer prevails, and the equilibrium position is insignificantlyt affected at variation of the electronic characteristics of the substituents in the aromatic ring.     

Synthesis of functional derivatives of aryl trichlorovinyl (trichloroallyl) ketones via consecutive transformations of the carbonyl group

An efficient procedure have been developed for the selective reduction of the carbonyl group in phenyl trichlorovinyl ketone and aryl trichloroallyl ketones by the action of NaBH₄ in propan-2-ol to obtain the corresponding alcohols. The hydroxy group in the latter was converted into amino by the Ritter reaction. Treatment of the alcohols and amines with 5-phenylisoxazole-3-carbonyl chloride and 4,5-dichloroisothiazole-3-carbonyl chloride gave the corresponding esters and amides, and condensation of the amines with aromatic aldehydes afforded Schiff bases.     

Condensation of β,δ-triketone derived from dehydroacetic acid with aliphatic amines and copper(II) complexes of the schiff bases

The condensation of ethyl-2-hydroxy-4-oxo-4-(4-hydroxy-6-methyl-2-pyrone-3-yl)-2-butenoate with primary aliphatic monoamines occurs at 4-hydroxy group of the pyrone ring according to ¹HNMR and mass spectrometric data. The ketamine tautomeric form of the prepared Schiff bases is predominantly present in chloroform solutions. Isolated crude copper(II) complexes of the condensation products are shown to be mononuclear with the 1:2 metal to ligand ratio.     

1-Hetaryltriazenes in the synthesis of condensed mesoionic 1,2,3-triazolio-5-olates

Condensed mesoionic 1,2,3-triazoles containing an aryl or hetaryl substituent at N₍₂₎ in the ring have been synthesized by intramolecular condensation. Dedicated to Academician M. G. Voronkov on his Eighty-Fifth Birthday. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1714–1719, November, 2006.     

N‐arylhexahydropyrimidines. Part 1. Synthesis and 1H NMR characterization of 1,3‐Di and 1,2,3‐trisubstituted derivatives

A series of N‐arylhexahydropyrimidines la‐1 were synthesized by condensation of N‐aryl‐N'‐alkyl‐ (or aryl)‐1,3‐propanediamines 2a‐h with aldehydes. Reactions with formaldehyde proceeded in hydroalcoholic solution, while condensation with aromatic aldehydes required in general the use of activated molecular sieves. ¹H NMR spectra of compounds la‐1 were analyzed and the results correlated with their conforma‐tional features. Derivatives devoid of a 2‐substituent la‐g show fast ring reversal and N‐inversion. The presence of a 2‐aryl group shifts the ring reversal equilibrium towards conformations where the 2‐aryl substituent is equatorial. Differential assignment of axial and equatorial hydrogens in these compounds was made on the basis of coupling constants and chemical shift values. In compound 1k spectral data suggest the axial orientation of the N‐methyl group. Such findings were confirmed in the corresponding NOESY spectrum.     

β-thioxo esters—II : Evidence for ester group rotamerism and pertubation of the intramolecular hydrogen-bonding in enethiolized 2-thioxo cycloalkanecarboxylic esters

Ethyl 2-thioxo cycloalkanecarboxylates of ring sizes 5–9 exist in CCl₄ solution in the tautomeric cis-enethiol form, whereas the 10–12 membered ring compounds exist as an equilibrium mixture of several tautomeric forms. On the basis of NMR and IR spectral data it is concluded that the cis-enethiols exist as equilibrium mixtures of two rapidly interconverting rotameric forms, one involving intramolecular H-bonding, the other having the ester group rotated through 180° so that the ester carbonyl group is unable to form an intramolecular H-bond, although still conjugated with the enethiolic double bond. The relative equilibrium concentrations at ～35° of the two rotameric cis-enethiol forms have been determined for all investigated compounds.     

Tautomerism of 5-hydroxy-1,4-naphthoquinone-4-imines

The existence of tautomeric equilibrium in solutions of 5-hydroxy-1,4-naphthoquinone-4-imines between the p-quinoid and ana-quinoid forms was proven by electronic, PMR and NMR (¹⁴N) spectroscopy. It was found that replacement of the aryl group at the nitrogen atom of the imino group by an alkyl group, and also proton-donor solvents forming hydrogen bonds with the oxygen attached at the C₅ atom cause a shift of the tautomeric equilibrium in the direction of the ana-quinoid form.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2572–2576, November, 1989.