I. V. Dorogan

New method for the synthesis of β-tropolones : Structures of condensation products of o-quinones with 2-methylquinolines and the mechanism of their formation

A new method was developed for the synthesis of functionalized β-tropolones based on acid-catalyzed condensation of 2-methylquinoline derivatives with 3,5-di(tert-butyl)-1,2-benzoquinone and 4,6-di(tert-butyl)-3-nitro-1,2-benzoquinone (14). The mechanism of the multistep reaction giving rise to β-tropolones and their tautomerism were studied by quantum chemical methods (DFT B3LYP/6-31G**). The reaction of 2-methylquinoline derivatives containing the tertiary amino group at position 4 with quinone 14 is accompanied by the formation of derivatives of a new heterocyclic system, viz., 4,6-dioxo-2-azabicyclo[3.3.0]octa-2,7-diene N-oxide. The molecular and crystal structures of two 5,7-di(tert-butyl)-3-hydroxy-2-(quinolin-2-yl)tropolones and two dioxoazabicyclooctadiene N-oxides, as well as of the preparatively isolated intermediate of the first condensation step and of the by-product of the reaction were established by X-ray diffraction.

Synthesis, Photophysical and Redox Properties of the D–π–A Type Pyrimidine Dyes Bearing the 9-Phenyl-9H-Carbazole Moiety

Novel donor-π-acceptor dyes bearing the pyrimidine unit as an electron-withdrawing group have been synthesized by using combination of two processes, based on the microwave-assisted Suzuki cross-coupling reaction and nucleophilic aromatic substitution of hydrogen. Spectral properties of the obtained dyes in six aprotic solvents of various polarities have been studied by ultraviolet–visible and fluorescence spectroscopy. In contrast to the absorption spectra, fluorescence emission spectra displayed a strong dependence from their solvent polarities. The nature of the observed long wavelength maxima has been elucidated by means of quantum chemical calculations. The electrochemical properties of these dyes have been investigated by using cyclic voltammetry, while their photovoltaic performance was evaluated by a device fabrication study. The experimental and calculation data show that all of the dyes can be regarded as potentially good photosensitizers for dye-sensitized solar cells.

New photochromic nonsymmetric bis-spiropyran of the 2,3-dihydro-4-oxonaphtho[2,1-e][1,3]oxazine series

New nonsymmetric bis-spiropyran of the 2,3-dihydro-4-oxonaphtho[2,1-e][1,3]oxazine series was prepared. On the basis of the results of photochemical study and quantum-chemical calculations, it has been shown that both pyran cycles experience opening during irradiation of a bis-spiropyran solution with unfiltered light.

2-Hetaryl-1,3-tropolones based on five-membered nitrogen heterocycles: synthesis, structure and properties

Summary A series of derivatives of 2-hetaryl-1,3-tropolone (β-tropolone) was prepared by the acid-catalyzed reaction of 2-methylbenzoxazoles, 2-methylbenzothiazoles and 2,3,3-trimethylindoline with 3,4,5,6-tetrachloro-1,2-benzoquinone. The molecular structures of the three representative compounds were determined by X-ray crystallography. In crystal and (as shown by the DFT PBE0/6-311+G** calculations) in solution, 2-hetaryl-4,5,6,7-tetrachloro- and 2-hetaryl-5,6,7-trichloro-1,3-tropolones exist in the NH-tautomeric form with a strong resonance-assisted intramolecular N–H···O hydrogen bond. The mechanism of the formation of 1,3-tropolones in the reaction of methylene-active five-membered heterocycles with o-chloranil in acetic acid solution has been studied using density functional theory (DFT) methods. The reaction of 2-(2-benzoxa(thia)zolyl)-5,6,7-trichloro(4,5,6,7-tetrachloro)-1,3-tropolones with alcohols leads to the contraction of the seven-membered tropone ring with the formation of 2-(2-benzoxa(thia)zolyl)-6-alkoxycarbonylphenols. The molecular structure of 2-(2-ethoxycarbonyl-6-hydroxy-3,4,5-trichlorophenyl)benzoxazole has been determined by X-ray diffraction. 2-(2-Benzoxa(thia)zolyl)-6-alkoxycarbonylphenols display intense green fluorescence with anomalous Stokes shifts caused by the excited state intramolecular proton transfer (ESIPT) effects.

Synthesis and structure of 3-arylamino-2-(quinolin-2-yl)tropones

A reaction of substituted 2-(quinolin-2-yl)-1,3-tropolones with POCl3 leads to the new3-chloro-2-(quinolin-2-yl)tropone derivatives. New 2-(4-arylaminoquinolin-2-yl)-3-aryl-aminocyclohepta-2,4,6-trien-1-ones and 2-[4-morpholino(piperidino)quinolin-2-yl]-3-aryl-aminocyclohepta-2,4,6-trien-1-ones were obtained by nucleophilic substitution reaction of the halogen atom in 2-(4-chloroquinolin-2-yl)-3-chlorotropones and 3-chloro-2-[4-morpholino-(piperidino)quinolin-2-yl]tropones. Molecular structures of 3-chloro-2-(quinolin-2-yl)tropone and 3-arylamino-2-(quinolin-2-yl)tropone were established by X-ray diffraction analysis. Energy and structural characteristics of isomers of 3-arylamino-2-(quinolin-2-yl)tropones in the gas phase and in solution were calculated by the density functional theory method (PBE0/6-31G**).

Synthesis and structure of heterocyclic derivatives of pyran-2-ones based on the dimer of 4,6-di(tert-butyl)-3-hydroxy-1,2-benzoquinone

Acid-catalyzed reaction of 6,10a-dihydroxy-3,4a,7,9-tetra(tert-butyl)-1,2,4a,10a-tetrahydrodibenzo-[b,e][1,4]dioxine-1,2-dione with 2-methylquinoline derivatives led to the formation of a previously unknown system 6-[(Z)-2-(quinolin-2-yl)-1-hydroxyethen-1-yl]pyran-2-one. The molecular structure of 3,5-di(tert-butyl)-6-[(Z)-2-(7,8-dimethyl-4-chloroquinolin-2-yl)-1-hydroxyvinyl]pyran-2-one was established by XRD method; the energy and structural characteristics of its isomers in the gas phase and in a polar solvent were calculated by quantumchemical methods (B3LYP/6-31G**).

COMPUTATIONAL MODELING OF THE MECHANISMS OF CIRCUMAMBULATORY REARRANGEMENTS OF MAIN-GROUP MIGRANTS IN THE CYCLOPROPENE RING

Abstract Reaction pathways for circumambulatory rearrangements of main-group-centred migrants (NO, PO, NCS, SCN, NCO, OCN, SR, Cl, Br and XCHX, where X is CH 2 , NH, O, S) around the periphery of a cyclopropene ring have been studied computationally by use of semiempirical (MNDO/PM3 and AM1) and ab initio (RHF, MP2) methods. In contrast to the rearrangements of similar cyclopentadiene derivatives, the mechanism of consecutive 1,2-shifts was found to be highly energy-consuming for all the cyclopropenes under study. The rearrangements of cyclopropenes containing electronegative migrating groups readily acquiring a negative charge (Cl, Br, NCS, SCN, etc.) occur preferably through an ionization-recombination pathway, whereas circumambulation of allyl and heteroallyl groups is governed by the 3,3-sigmatropic shift mechanism. For the migration of the XCHX groups (X is CH 2 , NR, O, S), the potential energy surfaces in the vicinity of the transition state structures are flat and contain local minima related to biradical intermediates and cage-type structures. The results obtained are compared with the experimental data available and earlier calculations of circumambulatory rearrangements of cyclopentadienes with the same migratory groups.

Synthesis and structure of 2-(4′-oxo-3H-quinazolin-2′-yl)-1,3-tropolone

The acid-catalyzed condensation of 2-methyl-4-oxo-3H-quinazolin with 3,5-di(tert-butyl)-1,2-benzoquinone affords 5,7-di(tert-butyl)-2-(4′-oxo-3H-quinazolin-2′-yl)-1,3-tropolone and 2-(3,5-di(tert-butyl)-2-hydroxybenzoyl)-3H-quinazolin-4-one. The molecular structures of 5,7-di(tert-butyl)-2-(4′-oxo-3H-quinazolin-2′-yl)-1,3-tropolone and 2-(3,5-di(tert-butyl)-2-hydroxybenzoyl)-3H-quinazolin-4-one were studied by X-ray diffraction, two-dimensional NMR spectroscopy, and the density functional theory (PBE0/6-311+G**).

Synthesis and molecular structure of 3-[5-(quinolin-2-yl)penta-1,4-dien-1-yl]-1,4-benzodioxin-2-one

Acid-catalyzed reaction of 6,10a-dihydroxy-3,4a,7,9-tetra(tert-butyl)-1,2,4a,10a-tetrahydrodibenzo-[b,e][1,4]dioxine-1,2-dione with 4-chloro-2,7,8-trimethylquinoline gave previously unknown 3,6,8-tri-tert-butyl-3-[2-tert-butyl-5-(4-chloro-7,8-dimethylquinolin-2-yl)-4-hydroxy-3-oxopenta-1,4-dien-1-yl]-5-hydroxy-1,4-benzodioxin-2-one whose structure was determined by X-ray analysis. The energy and structure parameters of possible isomers of the product in the gas phase and in solution were estimated by PBE0/6-31G** quantum-chemical calculations.

Synthesis, structure, and photoluminescence properties of bis[2-(1,3-benzoxazol-2-yl-κN)-4,5-dichloro-3-(ethoxycarbonyl)phenolato-κO]zinc(II)

The structure of bis[2-(1,3-benzoxazol-2-yl-κN)-4,5-dichloro-3-(ethoxycarbonyl)phenolato-κO]-zinc(II) was determined by IR and 1H and 13C NMR spectroscopy, and its structural characteristics were estimated by quantum chemical calculations. The complex showed photoluminescence properties.