Vol 54, No 4 (2018)

Salicylaldehydes containing a tert-butyl or 2-phenylpropan-2-yl group in the 3-position reacted with N,N-diallyl-p-and -m-phenylenediamines in methanol to give the corresponding Schiff bases which were used as ligands to obtain titanium(IV) complexes with the composition L₂TiCl₂ by reaction with diisopropoxytitanium dichloride.

Dialkyl 3,4-dihydroxyhexa-2,4-dienedioates reacted with substituted anilines and aromatic aldehydes or with the corresponding Schiff bases to give 5-(2-alkoxy-2-oxoethyl)-1,2-diaryl-4-hydroxy-1H-pyrrole- 3-carboxylates.

New salt structures have been synthesized from pyridoxal and various organic and inorganic acids.

Isonicotinic acid ethyl ester reacted with substituted phenacyl bromides to give the corresponding quaternary salts which were reduced with sodium tetrahydridoborate to ethyl 1-(2-aryl-2-hydroxyethyl)-1,2,3,6- tetrahydropyridine-4-carboxylates. The presence of an electron-donating substituent in the benzene ring of the latter is a necessary condition for their acid hydrolysis with cleavage of the C–N bond and formation of isoguvacine. Analogous derivatives with electron-withdrawing substituents are not converted to isoguvacine under similar conditions.

The condensation of 1-amino-3,3-dimethyl-3,4-dihydronaphthalene-2-carbonitrile with chloroacetyl chloride afforded chloro-N-(2-cyano-3,3-dimethyl-3,4-dihydronaphthalen-1-yl)acetamide which underwent cyclization to 2-(chloromethyl)-5,5-dimethyl-5,6-dihydrobenzo[h]quinazolin-4(3H)-one. The latter reacted with various nucleophiles (alkali metal alkoxides, piperazine, 2-sulfanylethanol) to give 2-(alkoxymethyl)-, 2-(piperazin-1-ylmethyl)-, and 2-{[(2-hydroxyethyl)sulfanyl]methyl}-5,5-dimethyl-5,6-dihydrobenzo[h]quinazolin- 4(3H)-ones. The condensation of 2-(chloromethyl)benzo[h]quinazoline with 2-thioxo derivatives of quinazoline and benzo[h]quinazolines led to the formation of bis-quinazolines in which 5,5-dimethyl-5,6- dihydrobenzo[h]quinazolin-4(3H)-one fragment is linked to quinazoline or benzo[h]quinazoline system through a CH₂S bridge.

Dialkyl [(3,5-di-tert-butyl-4-oxocyclohexa-2,5-dien-1-ylidene)methyl]phosphonates reacted with phenol and benzenediols in the presence of trifluoromethanesulfonic acid to give products of electrophilic substitution in the benzene ring, the corresponding diarylmethylphosphonates or [phenylenebis(arylmethylene)]- diphosphonates. The reaction of diphenyl [(3,5-di-tert-butyl-4-oxocyclohexa-2,5-dien-1-ylidene)methyl]phosphonate with 2-methylbenzene-1,3-diol at a ratio of 1: 1 afforded 3-(3,5-di-tert-butyl-4-hydroxyphenyl)-6-hydroxy-7-methyl-2-phenoxy-2,3-dihydro-1,2λ⁵-benzoxaphosphol-6-one.

Ethyl 2-amino-5-(2-aryl-2-oxoethylidene)-4-oxo-1H-4,5-dihydrofuran-3-carboxylates and 2-amino- 5-(2-aryl-2-oxoethylidene)-4-oxo-1H-4,5-dihydrofuran-3-carbonitriles reacted with alcohols in the presence of a catalytic amount of concentrated aqueous HCl to give the corresponding 5-alkoxy-2-amino-5-(2-aryl-2- oxoethyl)-4-oxo-1H-4,5-dihydrofuran-3-carboxylic acid derivatives. A probable reaction mechanism was proposed on the basis B3LYP/6-311G(d) quantum chemical calculations.

5-Substituted 2,6-dimethylpyrimidin-4(3H)-ones were synthesized, and their structure was proved by X-ray analysis. Their reactions with aromatic aldehydes regioselectively afforded (Z)-2-(2-arylethenyl)- pyrimidin-4(3H)-ones whose structure was determined by one- and two-dimensional (NOESY) ¹H NMR and X-ray analysis.

Two series of new adamantyl derivatives of polynitrogen heterocycles, 2-(adamantan-1-yl)-5-aryl- 1,3,4-oxadiazoles and 2-(adamantan-1-yl)-5-aryl-2H-tetrazoles, have been synthesized, and their structure has been determined by NMR spectroscopy, mass spectrometry, and X-ray analysis. Biological studies in vitro have revealed high inhibitory activity of some of the synthesized 2-(adamantan-1-yl)-5-aryl-2H-tetrazoles against H1N1 influenza A viruses in combination with a relatively low selectivity.

Conformational analysis of a fluoroethane molecule encapsulated in single-walled carbon nanotubes at the DFT PBE/3ζ level of theory showed that the force field of the nanotube considerably reduces the potential barrier to internal rotation about the C–C bond due to increase of the relative stability of the eclipsed or closely related pseudo-staggered conformer, which in some cases correspond to the energy minima. This is accompanied by shortening of the C–C and C–F bonds and appearance of an electric charge on the encapsulated molecule.

N-Methyl- and N,N-dimethylcycloalkanamines were synthesized by reaction of cycloalkanamines with dimethyl carbonate in the presence of NaY zeolite containing no binder. Optimal reactant and catalyst ratios and reaction conditions were found.

2-Acetyl-4-methyl-3,4-dihydropyrans reacted with hydroxylamine in pyridine to give (E)-1-(4-methyl-3,4-dihydro-2H-pyran-2-yl)ethan-1-one oximes in up to 85% yield with high stereoselectivity.

1-Aryl-3,4-dihydroxy-5-(3-methylquinoxalin-2-yl)penta-2,4-dien-1-ones were synthesized by reaction of 5-arylfuran-2,3-diones with 2,3-dimethylquinoxaline.

A new mechanochemical method has been proposed for the synthesis of some acetamides containing a cyclic fragment by reaction of primary cyclic amines with tetraacetylglycoluril.