E. V. Mironova

Tautomerism of aza cycles: II. Synthesis and structure of 5-substituted 3-(2-hydroxyethylsulfanyl)-1H-1,2,4-triazoles and their salts. Preference of the 1H,4H-1,2,4-triazolium tautomers

New complexing agents, potentially tautomeric 3-(2-hydroxyethylsulfanyl)-1H-1,2,4-triazole, its 5-methyl-and 5-phenyl-substituted analogs, and some their salts, were synthesized, and their structure was discussed on the basis of the 1H and 13C NMR, IR, and mass spectra, X-ray diffraction data, and published data. In keeping with the rule formulated previously for N-unsubstituted 1,2,4-triazoles having dissimilar substituents, the synthesized compounds were found to exist as 3-(2-hydroxyethylsulfanyl)-5-R-1H-1,2,4-triazole tautomers (3-RA-5-RD-1H-1,2,4-triazoly). They are protonated at the nitrogen atom in position 4 of the triazole ring. The 1H and 13C NMR spectra of these compounds in trifluoroacetic acid suggest the presence of two forms due to equilibrium between the neutral and protonated species. Analysis of the crystallographic data for the triazolium salts and published data showed preference of the 1H,4H-1,2,4-triazolium tautomer.

Tautomerism of aza cycles: I. Structure of 3(5)-butylsulfanyl-5(3)-methyl(phenyl)-1H-1,2,4-triazole tautomers in crystal. Preference of the 3-RA-5-RD-1H-tautomer of 3(5)-mono-and 3,5-disubstituted 1,2,4-triazoles

The X-ray diffraction study of potentially tautomeric 3(5)-butylsulfanyl-5(3)-methyl-1H-1,2,4-triazole and its 5(3)-phenyl-substituted analog showed that these compounds in crystal have the structure of 3-butylsulfanyl-5-methyl(phenyl)-1H-tautomers. Analysis of our experimental and published data indicated that 3(5)-monosubstituted 1,2,4-triazoles and 3,5-disubstituted derivatives having nonequivalent substituents in crystal as exist as a tautomer in which the electron-acceptor substituent (RA) occupies the 3 position, while the electron-donor substituent (RD) resides in the 5 position, i.e., as 3-RA-5-RD-1H-1,2,4-triazoles. Symmetric 3,5-disubstituted 1,2,4-triazoles could give rise to tautomeric equilibrium between the 1H-and 2H-structures even in crystal.

Rearrangement of Quinoxalin-2-ones When Exposed to Enamines Generated in Situ from Ketones and Ammonium Acetate: Method for the Synthesis of 1-(Pyrrolyl)benzimidazolones

The reaction of 3-benzoylquinoxalin-2(1H)-ones with enamines (generated in situ from ammonium acetate and the corresponding methylaryl(hetaryl)ketones) proceeds smoothly to give the corresponding substituted 1-(pyrrolyl)benzimidazolone derivatives in moderate yields through the novel rearrangement of 3-benzoylquinoxalin-2(1H)-ones involving a dual cleavage of the C3═N4 and C2-C3 bonds under mild conditions.

Planktonic ciliates of the Neva Estuary (Baltic Sea): community structure and spatial distribution

Ciliate communities in open waters of the meso-eutrophic Neva Estuary (the Baltic Sea) were studied in summer 2010. Abun- dance and biomass of ciliates were surprisingly low (0.03-1.9 ind ml -1 and 0.04-2.4 × 10 -3 μg C ml -1 ), especially in samples with high detritus content. During this study we detected four ciliate species which are new for the Baltic Sea. Mixotrophic ciliates dominated at the majority of stations (28-67% of overall ciliate numbers). Their contribution was signifi cantly higher in the outfall area and northern part of the Neva Estuary (Resort District), where total density of ciliates was low. Medium-sized ciliates (30-60 μm) were the most diverse and abundant (average contribution 59% of total abundance). The two parts of the estuary, separated from each other by a storm-surge barrier, differed slightly in their community structure (p < 0.05) but did not signifi cantly differ in ciliate numbers and biomass values.

Synthesis and steric structure of 3′,3′,5′-trimethyl-7′,7′-bis(trifluoromethyl)spiro[1,3,2-benzodioxaphosphole-2,1′-[2,6,8]trioxa[1λ5]phosphabicyclo[3.2.1]octane] and 3′,5′-dimethyl-7′,7′-bis(trifluoromethyl)spiro[1,3,2-benzodioxaphosphole-2,1′-[2,6,8]trioxa[1λ5]phosphabicyclo[3.2.1]oct[3]ene]

Reactions of hexafluoroacetone with 4-(1,3,2-benzodioxaphosphol-2-yloxy)-4-methylpentan-2-one and 4-(1,3,2-benzodioxaphosphol-2-yloxy)pent-3-en-2-one afforded cage spiro phosphoranes with a phosphorus-carbon bond, 3′,3′,5′-trimethyl-7′,7′-bis(trifluoromethyl)spiro[1,3,2-benzodioxaphosphole-2,1′-[2,6,8]-trioxa[1λ5]phosphabicyclo[3.2.1]octane] and 3′,5′-dimethyl-7′,7′-bis(trifluoromethyl)spiro[1,3,2-benzodioxaphosphole-2,1′-[2,6,8]trioxa[1λ5]phosphabicyclo[3.2.1]oct[3]ene], whose structure was determined by X-ray analysis.

2-chloro-3,3,5-trimethyl-2,3-dihydro-1,2λ5-oxaphosphole 2-oxide as precursor in a new synthesis of dialkyl(diaryl)-(2-methyl-4-oxopent-2-yl)phosphine oxides

A new approach has been developed to the synthesis of dialkyl(diaryl)(2-methyl-4-oxopent-2-yl)-phosphine oxides that are structural analogs of the drug dimephosphon. This approach is based on the reaction of 2-chloro-3,3,5-trimethyl-3H-1,2λ5-oxaphosphole 2-oxide with Grignard compounds, and it ensures high yields of the target products. The structure of bis(2-methoxyphenyl)(2-methyl-4-oxopent-2-yl)phosphine oxide was determined by X-ray analysis. (2-Methyl-4-oxopent-2-yl)dipropylphosphine oxide with magnesium bromide formed a 4: 1 complex whose structure was also determined by X-ray analysis.

Tautomerism of azacycles: III. Molecular and crystal structures of 3H-and 2-phenyl-1H,4H-4,5-dihydro-1,2,4-triazole-5-thiones

Compounds capable of tautomerism: sulfanyl-1,2,4-triazole, its C-phenyl derivative, and the crystal hydrate of the latter, were studied by single crystal X-ray diffraction. In the crystals they exist in the form of 3-R-1(H),4(H)-4,5-dihydro-1,2,4-triazole-5-thione with a considerable contribution of the bipolar structure. Published data on the tautomerism of sulfanyl-1,2,4-triazoles and their N-substituted analogs and on the correlation between the spectral characteristics and structures of sulfanyl-1,2,4-triazoles capable of tautomerism are discussed.

Formation of the cage-like phosphoranes with the P-C and P-N bonds in the reactions of 2-(2-benzylidenamino)phenoxy-4- tert -butylbenzo-1,3,2-dioxaphosphol with ethyl mesoxalate and ethyl trifluoropyruvate

The reaction of 2-(2-benzylidenamino)phenoxy-4-tert-butylbenzo-1,3,2-dioxaphosphol with ethyl mesoxalate and ethyl trifluoropyruvate resulted in the formation of tricyclic phosphoranes with the P-C and P-N bonds. The adduct emerged from the initial reaction of the PIII derivative with the activated ketone (1: 1), further underwent the transformation via the intramolecular reaction involving the benzylideniminoaryl substituent, which resulted in the formation of the cage-like phosphoranes.

Caged phosphorane with P-C bond based on chloral and 4,5-dimethyl-2-(2-oxo-1,2-diphenylethoxy)-1,3,2-dioxaphospholane

The key methods of caged phosphoranes synthesis are analyzed. Reaction of 4,5-dimethyl-2-(2-oxo-1,2-diphenylethoxy)-1,3,2-dioxaphospholane (prepared from the meso-form of 2,3-butanediol) with chloral has yielded the caged phosphorane containing a phosphorus-carbon bond: 1,1-(1,2-dimethylethylenedioxy)-3,4-diphenyl-6-trichloromethyl-2,5,7,1-trioxaphosphabicyclo[2.2.11,4]heptane; spatial structure of the product has been elucidated with X-ray diffraction analysis.

A novel acid-catalyzed rearrangement of 2-substituted-3-(2-nitrophenyl)oxiranes for the synthesis of di- and mono-oxalamides

A novel one-pot synthetic approach to N1-(2-carboxyaryl)-N2-(aryl or H)oxalamides from 3-(2-nitroaryl)oxirane-2-carboxamides via the classical Meinwald rearrangement and a new rearrangement sequence has been developed. The methodology is applicable to the synthesis of N-(2-carboxyphenyl)aryloxalmonoamides from (3-(2-nitrophenyl)oxiran-2-yl)(aryl)methanones. The method is operationally simple and high yielding, thus providing a new useful formula for both anthranilic acid derivatives and oxalamides.