Conformational effects in excited-state intramolecular proton transfer in <Emphasis Type="Italic">N</Emphasis>-substituted 2-(2-aminophenyl)-4H-3,1-benzoxazin-4-ones

The conformational effects in the ground and excited states were studied for N-substituted 2-(2-aminophenyl)-4H-3,1-benzoxazin-4-ones. The structural relaxation of the excited ESIPT product was revealed, which results in the formation of a nonplanar conformer undergoing efficient nonradiative deactivation. The aggregation of fluorophore molecules was observed in saturated hydrocarbons at low temperatures for N-substituted 2-(2-aminophenyl)-4H-3,1-benzoxazin-4-ones with the amido carbonyl group. Excited-state intramolecular proton transfer was not observed in this associate, and the fluorophore molecules were shown to occur in the nonplanar conformation, in which there is no intramolecular hydrogen bonding.     

Intramolecular photoinduced proton transfer in 2-(2-aminophenyl)-4H-3,1-benzoxazin-4-ones with different electron-withdrawing N-substituents

Fluorescence spectra of N-substituted 2-(2-aminophenyl)-4H-3,1-benzoxazin-4-ones consist of two bands, the long-wavelength band with anomalous Stokes shift, which corresponds to the emission of the product of intramolecular photoinduced proton transfer, and the short-wavelength band belonging to the form in which proton transfer does not occur. It is assumed that there is equilibrium between two planar rotamers in the ground state: one with the N-H…N hydrogen bond in which the intramolecular photoinduced proton transfer occurs and the other with the N-H…O bond, which does not experience hydrogen transfer. According to ab initio quantum-chemical calculations, the potential energy of proton transfer in the first excited singlet state has a potential barrier of 2.1–26.8 kJ/mol depending on the electron-withdrawing ability of the substituent on the amino group.     

Femtosecond dynamics of excited-state intramolecular proton transfer in <Emphasis Type="Italic">o</Emphasis>-tosylaminobenzaldehyde

Dynamics of excited-state intramolecular proton transfer (ESIPT) in o-tosylaminobenzaldehyde has been studied by femtosecond absorption spectroscopy with a time resolution of 30 fs. The characteristic time of this process is ∼100 fs. Differential absorption rate curves exhibit oscillations that are consistent with theoretically predicted ESIPT-promoting vibrational modes. Efficient nonradiative deactivation with a rate constant of 6.25 × 10¹⁰ s⁻¹ occurs in the excited product of proton transfer, with internal rotation followed by intersystem crossing being one of the feasible deactivation pathways.     

Synthesis and antibacterial activity of new <Emphasis Type="Italic">N</Emphasis>-substituted 7-amino-4-methyl-2<Emphasis Type="Italic">H</Emphasis>-chromen-2-ones

N-Substituted 7-amino-4-methyl-2H-chromen-2-ones containing one or two functionalized azole or azine moieties were synthesized. The structures of all synthesized compounds were confirmed by IR, ¹H NMR, and ¹³C NMR spectroscopy. Some of the synthesized compounds exhibited weak antibacterial activity against Rhizobium radiobacter, Escherichia coli, and Xanthomonas campestris.     

Ultrasound-accelerated one-pot synthesis of <Emphasis Type=Italic>N</Emphasis>-acetyl-2-aryl-1,2-dihydro-4<Emphasis Type=Italic>H</Emphasis>-3,1-benzoxazin-4-ones

The one-pot synthesis of N-acetyl-2-aryl-1,2-dihydro-4H-3,1-benzoxazin-4-one derivatives from the condensation reaction of anthranilic acids with heteroaromatic aldehydes in the presence of excess amount of acetic anhydride has been explored. The reactions proceed smoothly under ultrasound irradiation and without catalyst at 35 − 40 °C to afford the title products in high yields.     

Thiocyanation of <Emphasis Type="Italic">N</Emphasis>-arylsulfonyl-, <Emphasis Type="Italic">N</Emphasis>-aroyl-, and <Emphasis Type="Italic">N</Emphasis>-[(<Emphasis Type="Italic">N</Emphasis>-arylsulfonyl)benzimidoyl]-1,4-benzoquinone imines

Reactions of thiocyanate ion with N-aroyl-, N-arylsulfonyl-, and N-(N-arylsulfonylbenzimidoyl)-1,4-benzoquinone imines follow the 1,4-addition pattern, and the adducts undergo intramolecular cyclization to give the corresponding N-substituted 5-amino-1,3-benzoxathiol-2-ones as final products.     

Copolymer of <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-diallyl-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dimethylammonium chloride with maleic acid as drug carrier

A copolymer of N,N-diallyl-N,N-dimethylammonium chloride with maleic acid of constant composition was prepared under the conditions of radical initiation. The possibility of the functionalization of the copolymer with drugs containing amino groups by polymer-analogous transformations was examined. Conditions were found for preparing conjugates of the copolymer with isoniazid. The structures and the quantitative compositions of the conjugates were determined by ¹³С NMR spectroscopy, and the possibility of preparing conjugates with controlled drug content was demonstrated.     

Molecular properties of the copolymers of <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-diallyl-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dimethylammonium chloride and maleic acid

The hydrodynamic and conformational properties of molecules of poly(N,N-diallyl-N,N-dimethylammonium chloride) and N,N-diallyl-N,N-dimethylammonium chloride-maleic acid copolymers of different compositions in solutions with various ionic-strength and pH values, as well as of the polyelectrolyte complex based on the copolymer with dodecyl sulfate anions in chloroform, are studied. For poly(N,N-diallyl-N,N-dimethylammonium chloride) molecules in a 1 M NaCl solution, the Kuhn segment length and the hydrodynamic diameter of the chain are estimated as A = 3.9 nm and d = 0.48 nm, respectively. In acidic solutions with pH 3.5, the copolymers demonstrate behavior typical for polyelectrolytes. In an alkaline solution with pH 13, when 1 M NaCl is added to the solution of the copolymer containing 29 mol % maleic acid units, there is an antipolyelectrolyte effect that manifests itself as an increase in the intrinsic viscosity of the copolymer and in the hydrodynamic radius of its molecules. It is found that an increase in the fraction of maleic acid units in the copolymer from 12 to 42 mol % brings about a reduction in the equilibrium rigidity of its macromolecules from 4.1 to 2.2 nm. The equilibrium rigidity of polyelectrolyte-complex molecules is higher than that of initial copolymer molecules owing to steric interactions arising between the aliphatic chains of dodecyl sulfate anions. In an electric field, the molecules of the complex are oriented owing to the induced dipole moment resulting from the displacement of dodecyl sulfate anions along the chain contour.     

Synthesis of 2-amino-4H-3,1-benzoxazines and 2-amino-4H-3,1-benzothiazines by the rearrangement of <Emphasis Type="Italic">o</Emphasis>-cyclopropylphenylureas and <Emphasis Type="Italic">o</Emphasis>-cyclopropylphenylthioureas

Syntheses are reported for 2-cyclopropylphenylureas and 2-cyclopropylphenylthioureas and the behavior of these compounds was studied under conditions for the acid-catalyzed opening of the cyclopropyl ring. Upon the action of concentrated sulfuric acid or trifluoroacetic acid, these ureas and thioureas can undergo rearrangement to the corresponding 3,1-benzoxazines and 3,1-benzothiazines. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 115–126, January, 2008.     

Chemosensors based on <Emphasis Type="Italic">N</Emphasis>-(2-aminophenyl)-<Emphasis Type="Italic">N</Emphasis>-(9-anthrylmethyl)amine: II

A series of N-(9-anthrylmethyl)arylimines was prepared by condensation of N-(2-aminophenyl)-N-(9-anthrylmethyl)amine with aromatic aldehydes. The study of the luminescent and complexing properties of compounds obtained showed that 2-{[2-(9-anthrylmethylamino)phenylimino]methyl}-1-naphthol and 1-{[2-(9- anthrylmethylamino)phenylimino]methyl}-6-bromo-2-naphthol were efficient highly selective chemosensors of cations Hg²⁺.     

Conformations and properties of <Emphasis Type="Italic">O</Emphasis>-Alkyl-<Emphasis Type="Italic">S</Emphasis>-(2-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dialkylamino)-ethylmethylthiophosphonates

Conformers of the biologically active compounds CH₃P(O)(OR)(SCH₂CH₂NR ₂ ^′ ), where (I) R = i-C₄H₉, R′ = C₂H₅ and (II) R = C₂H₅, R′ = i-C₃H₇, are calculated within the AM1 level of theory. The elongated and twisted forms with maximum and minimum distances between a nitrogen atom and those of a phosphorus tetrahedron, respectively, and bearing a syn and anti oriented alkoxy group relative to a phosphoryl oxygen, are studied. It is found that the differences between the energy, electronic, and geometric parameters of these forms are apparent in differences between their properties, e.g., the ability to participate in complexation and protonation, reactions that to some extent simulate the interaction between a substance and a biological object.     

4H-3,1-Benzoxazin-4-ones methoxy-substituted 2-(2-arenesulfonylaminophenyl)-4H-3,1-benzoxazin-4-ones

Methoxy-substituted 2-(2-tosylaminophenyl)-4H-3,1-benzoxazin-4-one and 2-phenyl-4H-3,1-benzoxazin-4-one were synthesized. Their UV, IR, and luminescence spectra were studied. The position of the methoxy group affects the strength of the intramolecular hydrogen bond (IHB). The luminescence properties of methoxy-substituted 2-(2-tosylaminophenyl)-4H-3,1-benzoxazin-4-ones are associated with the strength of the IHB. The luminescence maximum is shifted to the short-wave region with strengthening of the IHB, and the luminescence intensity increase simultaneously.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1028–1032, August, 1971.The authors thank Yu. S. Ryabokobylko and A. O. Zisman for measuring the absorption spectra in the IR and UV regions.     

Synthesis of (<Emphasis Type="Italic">E</Emphasis>)-<Emphasis Type="Italic">N</Emphasis>-(3-alkoxy-4-acyloxyphenylmethylene)-<Emphasis Type="Italic">N</Emphasis>-(<Emphasis Type="Italic">e</Emphasis>-cyclohexyl)amines

Previously unknown E isomers of azomethines (Schiff bases) were synthesized from vanillal and vanillin esters by their reaction with cyclohexylamine.     

Synthesis of <Emphasis Type="Italic">N</Emphasis>-(2-aminoethyl)- and <Emphasis Type="Italic">N</Emphasis>-(3-aminopropyl)cytisine

2-(N-cytisinyl)acetamide or 3-(N-cytisinyl)propanamide were prepared by treatment of the methyl esters of N-cytisinylacetic or 3-(N-cytisinyl)propanoic acids with aqueous NH₄OH. N-(2-Aminoethyl)-or N-(3-aminopropyl)cytisine was synthesized by reduction of the amide with (i-Bu)₂AlH.     

Phosphorylation of <Emphasis Type="Italic">N</Emphasis>-glycosides derived from <Emphasis Type="Italic">para</Emphasis>-substituted aromatic amines

New carbohydrate-containing aminophosphoryl compounds were synthesized on the basis of glycosylamines. The reaction pathway suggested for addition of hydrophosphoryl compounds to N-glycosides was confirmed. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1986–1992, September, 2008.     

<Emphasis Type="Italic">N</Emphasis>-halohexamethyldisilazanes

The review is devoted to N-halohexamethyldisilazanes, perspective but scantily studied halogenating agents. Methods of preparation, physiochemical characteristics, and synthetic potential are considered. Mechanisms of a number of reactions are presented.     

<Emphasis Type="Italic">Z</Emphasis>-and <Emphasis Type="Italic">E</Emphasis>-conformers of <Emphasis Type="Italic">N</Emphasis>-chloroacetylcytisine

N-Chloroacetylcytisine was synthesized by acylation of (–)-cytisine. Stable Z- and E-conformers with respect to rotational isomerism around the N-12–CO bond were found in PMR spectra at room temperature. The point at which PMR resonances of the Z- and E-conformers coalesced upon heating was measured. The transition barrier between the conformers was estimated.     

Synthesis of amino acid conjugates of glycyrrhizic acid using <Emphasis Type="Italic">N</Emphasis>-hydroxyphthalimide and <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>'-dicyclohexylcarbodiimide

Synthesis of amino acid conjugates of glycyrrhizic acid with the use of N-hydroxyphthalimide, N,N'-dicyclohexylcarbodiimide, and tert-butyl esters of L-amino acids (valine, isoleucine, phenylalanine, and methionine) was performed followed by deprotection with trifluoroacetic acid. The target amino acid conjugates were isolated by column chromatography on silica gel in 40–45% yield. The structure of the prepared compounds was confirmed by IR and ¹³C NMR spectroscopy.     

Reactions of 1-nitrocyclohexene with <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-binucleophiles

A modification of 1-nitrocyclohexene synthesis is proposed; its reaction with phenylhydrazine and benzoic acid hydrazide is shown to afford monoadducts, and with hydrazine hydrate, bisaduct. With diphenylguanidine occurs heterocyclization to 1-phenyl-2-N-phenylamino-4,5,6,7-tetrahydrobenzimidazole, whose structure is confirmed by the X-ray diffraction data. The analysis performed for this compound of the electron density distribution function in the crystal made it possible to estimate the charge distribution, π-electrons delocalization nature, and the role of N-H…N, C-H…H-C and C-H…C interactions in the formation of the crystal packing.