O. S. Timofeev

Novel polycyclic pyrimidines

Methods are reported for preparing the novel pyrimidines 7,8-dihydro-9H-1,2,5-chalcodiazolo[3,4-d]thiazole[2,3-b]pyrimidin-4-ones and their N-oxides.

Mass spectrometry of macroheterocycles. 2. Characteristics of the fragmentation of azacrown ethers under electron impact

The fragmentation of aza-crown and diaza-crown ethers under electron impact was studied. It is shown that for the former the primary pathways of fragmentation of the molecular ions involve the intracyclic migration of a hydrogen atom and the elimination of C2H3O and CH2OH particles. A characteristic feature of the diaza-crown ethers is the ejection of a divinylaminyl radical.

Mass spectrometry of macroheterocycles. 1. Mass spectra of isomeric bicyclic crown ethers

The fundamental, fragmentation paths under electron impact of bridged crown ethers and the condensed, bicyclic crown ethers isomeric to them have been established by means of a combination of techniques (DADI, metastable defocusing, high resolution). The mass spectral criteria of the compounds in the series considered have been determined, as well as the characteristic ion peaks, the intensity of which permit the isomeric compounds to be distinguished.

Reactions of 3-(?-hydroxyethyl)-8-thiaxanthine

Depending on the base used, reaction of 3-(Β-hydroxyethyl)-8-thiaxanthine with p-toluenesulfonylchloride either stops at the stage of formation of the tosylate or gives 1,2,5-thiadiazolo[3,4-d]oxazolidino[2,3-b]pyrimidin-9(4H)-one. Upon treatment with ammonia or methylamine, both of these compounds react to give 3-(Β-hydroxyethyl)-8-thiaguanines.

CONFORMATION OF 4,5,6-SUBSTITUTED 2-ISOPROPYL-1,3,2-OXATHIOBORINANES

The configuration and predominant conformations of 2-isopropyl-4,5,6-alkylsubstituted 1,3,2-oxathioborinanes have been studied by 1H-NMR spectroscopy. 2,4-and 2,6-Dialkylsubstituted derivatives exist in near half-chair conformations, while 6,6-dimethyl-2-isopropyl-1,3,2-oxathioborinane exists in two energetically equivalent inverting forms. 2,5,6- and 2,4,6-Trialkylsubstituted 1,3,2-oxathioborinanes consist of mixtures of stereoisomers differing in the orientations of the alkyl groups at the C(6) and C(4) ring atoms.

Mass spectra of binuclear crown ethers

The mass-spectral analytical characteristics of binuclear crown ethers were established. The determining role of 1,5- and 1,4-C-H...O transannular interactions in the realization of rearrangement processes during fragmentation were ascertained.

Synthesis of nitro derivatives of dibenzo-18-crown-6

The reaction of dibenzo-18-crown-6 with nitric acid in the presence of lanthanum nitrate in acetontrile led to the production of its nitro derivative 20,25-dinitro-2,3,11,12-dibenzo-1,4,7,10,13,16-hexaoxacyclooctadeca-2,11-diene. Possible paths for the synthesis of the mono- and trinitro derivatives of dibenzo-18-crown-6 are analyzed.

Macroheterocycles. 32. Homolytic dehydrodimerization of crown ethers

The corresponding bis(crown ethers), as well as phenyl- and hydroxy-substituted crown ethers, were obtained by homolytic dehydrodimerization of 12-crown-4, 15-crown-5, and 18-crown-6 in benzene or water.