Cyclization of 1-thiocarbamoyl-2-phenylpyrazolidines

Thiocarbamoyl derivatives of N-phenylpyrazolidines are converted under the influence of acidic agents to mixtures of tetrahydropyrimido[2,1-b]benzothiazoles and 2-imino-3-aminoalkylbenzothiazoles and not only to tetrahydropyrimidobenzothiazoles, as previously assumed. The conditions for the predominant formation of tetrahydropyrimidobenzothiazoles were found. Deceased. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 228–233, February, 1980.     

Stereoselective synthesis of new spiro-fused heterocyclic systems, 2,3,4,4a,5.6-hexahydro-6H-spiro[benzo[<Emphasis Type="Italic">c</Emphasis>]quinolizine-5,4′-pyrazol]-5′-ones

The synthesis of 2,3,4,4a,5,6-hexahydro-6H-spiro[benzo[c]quinolizine-5,4′-pyrazol]-5′-ones has been achieved by the reaction of 2-piperidinobenzaldehydes with 2-aryl-5-methyl-2,4-dihydropyrazol-3-one via the “tert-amino effect” mechanism. On the 70th Birthday of Professor E. Lukevics. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 90–95, January, 2007.     

Stereoselective synthesis of spiro derivatives of 2,4-dimethyl-2,3,4,4a,5,6-hexahydro-6<Emphasis Type="Italic">H</Emphasis>-benzo[<Emphasis Type="Italic">c</Emphasis>]quinolizine

The reactions of 2-(3,5-dimethylpiperidino)benzaldehyde with Meldrum's acid and cyclohexane-1,3-dione occur as a tandem of the Knoevenagel condensation and cyclization promoted by the tert-amino effect. The cyclization yields only one isomer with the axial hydrogen atoms in positions 4 and 4a of the benzoquinolizine ring. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1492–1494, June, 2005.     

Synthesis and antiviral activity of nucleoside analogs based on 1,2,4-triazolo[3,2-<Emphasis Type="Italic">c</Emphasis>][1,2,4]triazin-7-ones

Nucleoside analogs containing hydroxybutyl, hydroxyethoxymethyl, allyloxymethyl, and propargyloxymethyl fragments were synthesized based on 1,2,4-triazolo[3,2-c][1,2,4]triazin-7-ones isosteric to purine bases. Some of the compounds obtained inhibit in vitro reproduction of influenza and respiratory syncytial virus infection.     

Regioselective reaction of ortho-piperidinobenzaldehydes with pyrazolone

Cyclization of 2-(4-R-piperidino)benzaldehydes with 5-methyl-2-phenyl-2,4-dihydro-3H-pyrazol-3-one proceeding via tert-amino effect mechanism is stereoselective. Relative configuration of (3R*,4aS*,5R*)-2,3,4,4a,5,6-hexahydro-1H-benzo[c]quinolizine was established on the base of NMR spectroscopy data and X-ray analysis.     

Fluorinated [1,2,4]triazolo[1,5-<Emphasis Type="Italic">a</Emphasis>]pyrimidines and [1,2,4]triazolo[5,1-<Emphasis Type="Italic">c</Emphasis>][1,2,4]triazines*

The reaction of 3-R-5-amino-1,2,4-triazoles with the ethyl ester of 2-fluoroacetoacetic acid gave 2-R-fluoro[1,2,4]triazolo[1,5-a]pyrimidin-7(4H)-ones. The reaction of a 3-R-1,2,4-triazolyl-5-diazonium salt with the ethyl ester of 2-fluoroacetoacetic acid and subsequent cyclization of the triazolylhydrazones lead to 7-R-3-fluoro[1,2,4]triazolo[5,1-c][1,2,4]triazin-4(1H)-ones.     

Diastereoselective synthesis of spiro derivatives of 3-substituted 2,3,4,4a,5,6-hexahydro-1<Emphasis Type="Italic">H</Emphasis>-benzo[<Emphasis Type="Italic">c</Emphasis>]quinolizines

The cyclization via the mechanism of “tert-amino effect” of 2-(4-R-piperidino)benzaldehydes with cyclic active methylene components (Meldrum’s acid, 1,3-cyclohexanedione, and N,N-disubstituted barbituric acids) proceeded stereoselectively giving spiro-joined 2,3,4,4a,5,6-hexahydro-1H-benzo[c]quinolizines with axially oriented hydrogen atoms in the positions 3 and 4a of the benzo[c]quinolizine ring.