Mass spectrometry of nitrogen heterocycles. 3. Thermal intramolecular cyclization of 2-azolylaminopyridines

Mass spectrometric fragmentation or decay of 2-azolylaminopyridines containing a carbonyl group in the ortho-position results in elimination of a neutral molecule (ammonia, ethanol, hydrogen sulfide). This decay process is accompanied by intramolecular cyclization to form an ion with a triazolo[1,5-a]pyrido[2,3-d]pyrimidine structure.For Communication 2, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 101–104, January, 1991.     

Unusual heterocyclization of chalcone podands with 3-amino-1,2,4-triazole

A new type of intramolecular cyclization of 1,5-bis[2-(E-3-oxo-3-phenylprop-1-enyl)-phenoxy]-3-oxapentane with 3-aminotriazole promoted by potassium ions was discovered. A cascade mechanism for the formation of crownophane with 4,7-dihydro[1,2,4]triazolo[1,5-a]-pyrimidine fragment was suggested. Effects of oligooxyethylene fragment of the chalcone podand and acid-base catalysis on the selectivity of the cyclocondensation processes and degree of oxidation of triazolopyrimidine fragments were studied. The product structures were confirmed by IR, ¹H and ¹³C NMR spectroscopy and X-ray diffraction study.     

Nitroazines. 8. Reactions of 6-nitroazolo[1,5-a]pyrimidines with pyrroles

The reactions of 6-nitroazolo[1,5-a]pyrimidines with pyrroles have been examined, and the influence of substitution in the azole moiety of the substrate on the course of the reaction studied. The formation of two isomeric sigma-adducts has been established by spectroscopy.For Communication 7, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1251–1255, September, 1988.     

Nitroazines. 10. Addition of polyatomic phenols to 6-nitroazolo[1,5-a]pyrimidines

Products of addition of polyphenols to 6-nitroazolo[1,5-a] pyrimidines without activation of the reagent and the substrate were obtained. The effect of substitution in the polyphenols and azolopyrimidines on the course of the process was examined.See [1] for Communication 9.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 811–816, June, 1989.     

Enantioselective microbial synthesis of (<Emphasis Type="Italic">S</Emphasis>)-7,8-difluoro-3,4-dihydro-3-methyl-2<Emphasis Type="Italic">H</Emphasis>-[1,4]benzoxazine

New strains of Rhodococcus erythropolis 25 and Microbacterium paraoxydans 20-11c actinobacteria were used to obtain (S)-7,8-difluoro-3,4-dihydro-3-methyl-2H-[1,4]benzoxazine (99.6% ee) by enantioselective microbial hydrolysis of the corresponding racemic N-acetyl derivative.     

Kinetic resolution of racemic 2-methyl-1,2,3,4-tetrahydroquinoline and its structural analogs by using 2-arylpropionyl chlorides

Acylation of 2-methyl-1,2,3,4-tetrahydroquinoline and 2-methylindoline with the acyl chlorides of naproxen, ibuprofen, and 2-phenylpropionic acid has been found to lead to efficient kinetic resolution with predominant formation of the (S,S)-(R,R)-diastereoisomers. The highest acylation stereoselectivity was found in toluene at -20°C. No significant kinetic resolution of N-(sec-butyl)aniline and 2-methylpiperidine was achieved by using 2-arylpropionyl chlorides.     

Synthesis of enantiomers of <Emphasis Type="Italic">N</Emphasis>-(2-aminopurin-6-yl)amino acids

Nonracemic N-(2-aminopurin-6-yl)-substituted amino acids were synthesized by nucleophilic substitution of chlorine atom in 2-acetamido-6-chloropurine upon treatment with amino acid tert-butyl esters and subsequent removal of protecting groups. Their enantiomeric composition was determined by HPLC on chiral stationary phases.     

Nitroazines 25. Spectral study of the reaction of the transformation of 6-Nitroazolo[1,5-a]Pyrimidines by CH-active nitriles

The methods of¹H and¹³C NMR and UV spectroscopy were utilized to investigate the structure of products of the transformation of 6-iiitroazolo[1,5-alpyritnidities by CH-active nitriles. The mechanism of the reactions is discussed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 235–239, February, 1994. Original article submitted December 20, 1993.