Vol 54, No 9 (2018)

New enantiomerically pure Schiff bases have been synthesized starting from (–)-3-bromocamphor and ethylenediamine, and their palladium chelates have been obtained.

A convenient procedure has been developed for the synthesis of (3-hydroxyadamantan-1-yl)-methanols on the basis of nitroxylation of adamantan-1-ylmethanols with fuming nitring acid and subsequent reduction of intermediate nitric acid esters with hydrazine hydrate. The title diols have also been obtained by the reduction of 1-nitroxy-3-(nitroxymethyl)adamantanes. The nitroxylation process is accompanied by oxidation with the formation of substituted adamantane-1-carboxylic acids.

2-Fluorophenyl isocyanate reacted with adamantan-1(2)-amines and their homologs in DMF to give 31–92% of the corresponding N,N′-disubstituted ureas that are target-oriented human soluble epoxide hydrolase (sEH) inhibitors. Introduction of a fluorine atom increases the sEH inhibitory activity by a factor of 4.5.

Oxidative dehydrogenation of pyrocatechol and 1,4-benzoquinone with 3,3′,5,5′-tetra-tert-butyl-trans-stilbenequinone as oxidant afforded oligomeric polyhydroquinones and polyquinones. Appropriate reaction conditions have been found, and the resulting oligomers have been characterized by IR and MALDI TOF mass spectra and elemental analyses.

Three-component condensation of heterocyclic chalcone analogs containing a thiophene ring with 5,5-dimethylcyclohexane-1,3-dione (dimedone) and ammonia at 140–145°C under pressure afforded functionalized 1,4,5,6,7,8-hexahydroquinoline derivatives; the corresponding triketones were formed under milder conditions (100–105°C). The condensation of 1,3-di(thiophen-2-yl)prop-2-en-1-one with dimedone and ammonia under harsh conditions unexpectedly produced functional 1,2,3,4,5,6,7,8,9,10-decahydroacridine derivative. Heterocyclic chalcone analogs reacted with ethyl acetoacetate in the presence of ammonia to give cyclocondensation products, ethyl 2-oxocyclohex-3-ene-1-carboxylates.

4-Oxo-3,4-diphenylbutane-1,1,2,2-tetracarbonitrile reacted with aliphatic, aromatic, and heterocyclic aldehydes in the presence of ammonium acetate to afford previously unknown iminofuran derivatives, 5-imino-4-(2-oxo-1,2-diphenylethyl)tetrahydrofuran-3,3,4-tricarbonitriles.

A series of ferrocenyl-substituted methyl ketones and chalcones were synthesized and converted to unsymmetrical 4,6-disubstituted pyrimidin-2-amines and 2-(1H-pyrrol-1-yl)pyrimidines in which the ferrocene fragment is separated from the pyrimidine ring by π-deficient (pyridine) or π-excessive (thiophene) heterocycle. The forbidden band gap of the obtained compounds was determined on the basis of their UV spectra (\(E_{\text{g}}^{\text{opt}}\) = 1.75‒2.36 eV), and their electrochemical properties were studied. The presence of a thiophene ring between the ferrocene and pyrimidine fragments reduces the redox potential of the ferrocene fragment (20‒30 mV), whereas pyridine spacer between the ferrocene and pyrimidine fragment increases the redox potential of the ferrocene fragment by more than 100 mV.

A new procedure has been developed for preparative synthesis of 3,4-dihydropyrimido[1,2-a]-benzimidazol-2(1H)-ones by thermal intramolecular heterocyclization of 3-[2-(propylsulfanyl)- and 2-(benzylsulfanyl)-1H-benzimidazol-1-yl]propanehydrazides and 3-[2-(benzylsulfanyl)-1H-benzimidazol-1-yl]-propanamide.

A one-pot preparative synthesis of 9-substituted 2-alkyl(aryl)imidazo[1,2-a]benzimidazole-3-carbonitriles from the corresponding 3-carbaldehydes and hydroxylamine O-sulfonic acid has been developed.

Reactions of 5-substituted 3-(arylmethylidene)furan-2(3H)-ones with hydrazine hydrate, hydroxylamine, and guanidine involved opening of the furanone ring. Their hydrazinolysis under mild conditions afforded acyclic 4-oxoalkanoic acid hydrazides which underwent heterocyclization to substituted pyridazinones in boiling ethanol. The presence of an alkyl substituent in the 5-position of the initial furanone favored heterocyclization with the formation of pyrazolidinone derivatives. The reactions of 3-(arylmethylidene)furan-2(3H)-ones with hydroxylamine and guanidine also produced new six-membered heterocycles, 2H-1,2-oxazin-3(4H)-ones and 4,6-disubstituted 3,4-dihydrofuro[2,3-d]pyrimidin-2-amines, respectively.

Intramolecular cyclization of 2-{[(4-methyl(or 4,6- and 4,8-dimethyl)quinolin-2-yl)sulfanyl]-acetyl}-N-phenylhydrazine-1-carbothioamides in alkaline and acidic media afforded {[(4-methyl(or 4,6- and 4,8-dimethyl)quinolin-2-yl)sulfanyl]acetyl}-substituted 1,2,4-triazoles and 1,3,4-thiadiazoles. The reaction of these compounds with ethyl bromoacetate gave thiazolidinone derivatives.

3,11-Dihydroxy and 3,11-dioxo triterpenoids of the fusidane series reacted with acrylonitrile in 1,4-dioxane in the presence of alkali and phase-transfer catalyst to give mono- and bis(2-cyanoethoxy) and 2-cyanoethyl derivatives. The reaction with 3,11-dioxo analog afforded 2,2-disubstituted derivative as a result of addition of two cyanoethyl groups to the α-position with respect to the C³=O carbonyl group. The isolated compounds were screened for antibacterial and antifungal activities.

A series of new 10-substituted 1,8-dinitro-3-oxa-5,10-diazatricyclo[6.3.1.0^2,6]dodeca-2(6),4-dienes have been synthesized by Mannich condensation of the hydride adduct of 5,7-dinitro-1,3-benzoxazole.

The ene reaction of pulegone with 4-phenyl-3H-1,2,4-triazole-3,5(4H)-dione, apart from the two previously described products, epimeric 1-[(1S,4R)- and 1-[(1R,4R)-4-methyl-2-oxo-1-(prop-1-en-2-yl)cyclohexyl]-4-phenyl-1,2,4-triazolidine-3,5-diones, gave one more isomer, 1-{1-methyl-1-[(4R)-4-methyl-6-oxocyclohex-1-en-1-yl]ethyl}-4-phenyl-1,2,4-triazolidine-3,5-dione. The latter is formed as a result of addition of 4-phenyl-3H-1,2,4-triazole-3,5(4H)-dione to the Me₂C= carbon atom of pulegone (anti-Markovnikov addition) and double bond migration to the six-membered carbocycle.