Valery F. Traven

NIR-fluorescent coumarin-fused BODIPY dyes with large Stokes shifts

A series of novel non-symmetrical coumarin-fused BODIPY dyes were synthesised. Their absorption and emission properties are strongly influenced by substitution in the coumarin moiety. Diethylamino-substituted dyes showed near-IR emission with large Stokes shifts (up to 144 nm) and good fluorescence quantum yields.

Polymethine dyes derived from boron complexes of acetylhydroxycoumarins

Novel dyes were obtained by condensation of boron derivatives of 3-acetyl-4-hydroxy- or 7-hydroxy-8-acylcoumarin with triethyl orthoformate or Fischers aldehyde. The reaction of the former boron complexes with DMF followed by condensation of the resultant hemicyanine with dimethylquinolinium iodides furnished non-symmetric polymethine dyes with a quinoline as the terminal heterocyclic unit.

A New Short Way to Furocoumarins

The Fries rearrangement of hydroxycoumarin chloroacetates provides a new short way to furocoumarins. 7-Hydroxycoumarin chloroacetates have been transformed in the presence of AICI3 into the proper dihydrofuro[2,3-h]coumarin-9-ones in high yields. 8-Substituted-7-hydroxycoumarin chloroacetates undergo into dihydrofuro[2,3-g]coumarin-6-ones in the presence of A1C13. 4Hydroxycoumarin chloroacetate has been transformed into the dihydrofuro[2,3-c]coumarin-3-one in the same conditions. Reduction of all dihydrofurocoumarinones followed by dehydration provide the proper furocoumarins in good yields. This new way to furocoumarins is mostly suitable for angelicin derivatives synthesis. All new coumarin derivatives have been characterised by NMR and mass spectra. Introduction Derivatives of the 2H-l-benzopyran-2-one (coumarin) belong to one of the most widespread classes of natural products. Many of them show a significant biological activity. For example, some furocoumarins (e.g. psoralens and angelicins) are useful in treatment of human skin diseases (1,2). Even though several methods for the preparation of unsubstituted in furan ring furocoumarins have been elaborated (3-13), some of these methods provide rather low yields, others have laborious procedures to carry out. Some schemes to furocoumarins contain a step of furan ring formation in strong alkaline solution, others include decarboxylation step. Both steps take place at the high temperatures and do not provide good yields of final products. We reported previously a new way to 4-methylangelicin based on transformation of 7-hydroxy-8bromoacetyl-4-methylcoumarin (14). After cyclization of the latter we have prepared 4methyldihydrofuro[2,3-h]coumarin-9-one. Reduction of the 4-methyldihydrofuro[2,3-h]coumarin-9-one followed by a dehydration step has resulted the angelicin derivative. In this paper we report a new way to dihydrofurocoumarinones excluding halogenation step. Chloroacetoxycoumarins undergo a Fries rearrangement with formation of the corresponding dihydrofurocoumarinones. This unusual Fries reaction provides a convenient short synthesis of furocoumarins. It involves three steps only (starting from chloroacetoxycoumarins) and goes in the most cases with good yields of final products.

HeI photoelectron spectra and structure of 4-hydroxycoumarin

Abstract The HeI photoelectron spectra of 4-hydroxycoumarin, 4-ethoxycoumarin and 3,3-dimethyl-2,4-chromandione have been measured. The ionization bands in the spectra have been assigned on the basis of semi-empirical (MNDO, AM1, PM3) and non-empirical (program Gaussian 94 with 6-31G* basis sets) quantum chemical calculations. Ionizations of two tautomeric forms — 2,4-chromandione and 4-hydroxychromen-2-one have been proposed in the photoelectron spectrum of 4-hydroxycoumarin.

UNUSUAL ONE-POT "SUBSTITUTION" OF 3- ACETYL AND 3- ETHOXYCARBONYL FUNCTIONS FOR CYANO GROUP IN COUMARINS

Interaction of 3-ethoxycarbonyl and 3-acetylcoumarins with cyanoacetylhydrazide or its N-acetyl and N-ethoxycarbonyl derivatives in the Michael reaction condit ions results in corresponding 3-cyanocoumarins . Apparently the reaction undergoes through pyrone ring opening and recyclization steps. Possible mechanism of the subst i tut ion is discussed. Introduction Some basecatalyzed coumarin reactions go through pyrone ring opening and recyclization steps (1-3). Coumar ins which contain electron acceptor groups like acetyl, benzoyl, cyano, ethoxycarbonyl funct ions at posit ion 3 react with different Cnucleophiles to produce 4-substi tuted 3 ,4-dihydrocoumarins or their t ransformation products. Thus 3-acetyl, 3-ethoxycarbonyl and 3-cyanocoumar ins yield Michael reaction products (Scheme 1) when react with cyanoacetamide or malonic ester monoamide. (4,5).

THE BASE-CATALYZED CYCLIZATION OF ACYLMETHYL ETHERS OF 7-HYDROXYCOUMARINS

We have studied the base-catalyzed cyclization of acylmethyl ethers of 7hydroxycoumarins which proceeds via lactone ring opening and yields psoralen derivatives. Corresponding cinnamic acid derivatives have been isolated The cyclization is a highly regioselective reaction, producing only linear furocoumarins. According to MNDO calculations, the anionic σ-complex formed due to acylmethyl attack to the C-6 position of the coumarin turns out to be more stable than that to the C-8 position. A series of new psoralens with phenyl group in the lactone and (or) in the furan ring have been synthesized and characterized by NMR and mass spectra. Introduction Cyclization of the acylmethyl ethers of 7-hydroxycoumarins 1 in the presence of a base has been found to be one of the most convenient routes to psoralen derivatives 2 (4) which are important compounds because of their photo chemical and photo biological activity (1-3). We used a base-catalyzed cyclization of 1 to synthesize psoralen derivatives 2, which have a phenyl group as substituent in the lactone and (or) in the furan ring. These psoralen derivatives seem to be prospective substrates in search of new photochemotherapeutic agents. We now report new results that deal with the mechanism of this reaction. Some intermediates of the reaction were isolated. Regioselectivity of the base-catalyzed cyclization of 1 was studied by the MNDO calculations of relative stability of the corresponding intermediate anionic σ-complexes.

A new (TTF)11I8 organic molecular conductor: from single crystals to flexible all-organic piezoresistive films

This paper reports selective synthesis of two iodine-containing TTF (tetrathiafulvalene) salts: one, (TTF)11I8, is a new molecular conductor while another is the known non-conducting (TTF)I3 compound. Single crystals of both salts were prepared using different amounts of iodine in the redox process between TTF and I2. X-ray data showed that the resulting conducting (TTF)11I8 salt might be considered as a new modulated phase of the non-stoichiometric (TTF)I0.7+δ salts. The electrical resistance of single crystals of (TTF)11I8 reveals a semiconducting-like behaviour. The paper presents also a study of electromechanical properties of organic conductive bi-layer (BL) films prepared by covering different organic polymeric films with a thin network of oriented submicrocrystals of (TTF)I0.7+δ phases. These BL films exhibit a combination of flexibility, lightweight, and high piezo-resistivity properties showing therefore a potential interest for electronic sensing applications where lightweight, large area coverage and flexibility are required.

Z/E (C=C)-isomerization and fluorescence modulation of imines of 7-N,N-dialkylamino-4-hydroxy-3-formylcoumarins in organic solvents

Abstract Imines of 7-dialkylamino-3-formyl-4-hydroxycoumarins have been found to exist in Z-ketoenamine form in crystal state and undergo Z/E-isomerization around C=C bond in organic solvents at room temperature. Activation energies of isomerization have been measured experimentally and calculated by the DFT B3LYP method. Transition of ketoenamine form of p-nitrophenylimines into (hydroxy)imine form at low concentration (10-5 m) in polar solvents is accompanied by strong increase in fluorescence.

Opening of furanone ring of 2,3-dihydrofuro[3,2-c]coumarin-3-one derivatives by arylhydrazines

Abstract 2-Benzyliden-2,3-dihydrofuro[3,2-c]coumarin-3-one derivatives smoothly form corresponding hydrazones upon interaction with phenylhydrazinium chloride. However, when treated with phenylhydrazine base, these compounds undergo furanone ring opening and osazone formation.

Unusual transformation of 4-methyldihydrofuro[2,3-h]coumarin-9-one oxime in presence of Beckmann rearrangement catalysts

The rearrangement of 4-methyldihydrofuro[2,3-h]coumarin-9-one oxime in presence of Beckmann catalyst (mixture of glacial acetic acid with HCl or HBr ) or POCI3 provides corresponding 8halogeno-4-methyldihydrofuro[2,3-h]coumarin-9-ones formation. α-Halogenation of condensed furanone ring seems to be due to imin-amin tautomerism of the oxime. 8-Halogeno-4-methyldihydrofuro[2,3-h] coumarin-9-ones have been transformed to 9-acetoxy-8-halogeno-4-methylangelicins (due to their ketoenol tautomerism) and to 8-substituted derivatives (due to their reactivity with nucleophiles). Introduction Two ways of Beckmann rearrangement are known since it was discovered in 1886 (1). Normal way of Beckmann rearrangement of ketoximes provides a carboxylic acid amide formation via simultaneous intramolecular mechanism. Abnormal way of Beckmann rearrangement undergoes through intermediate carbocation and nitril formation (2-6). Beckmann rearrangements of cyclic oximes are also known. For example, oxime 1 gives two cyclic lactam isomers 2 and 3 under different reaction conditions (7).