Dusan Loos

Effect of Microwave Irradiation on the Condensation of 6-Substituted 3-Formylchromones with Some Five-membered Heterocyclic Compounds

Central Laboratories, Faculty of Chemical Technology, Slovak University of Technology, SK-812 37Bratislava, Slovak RepublicReceived: 14 November 1999 / Accepted: 31 December 1999 / Published: 19 February 2000Abstract: Different types of 3-substituted 4H-4-oxobenzopyrans were prepared by micro-wave irradiation as well as by a classical method. The beneficial effect of microwave irra-diation on the aldol condensation of 3-formylchromones with 2-imino-1-methyl-imidazolidine-4-one (creatinine), 2-thioxoimidazolidine-4-one (thiohydantoin) and 2-ethyl-2-thioxothiazolidin-4-one (3-ethylrhodanine) in different reaction media is described. Ourresults show that the effect of microwave irradiation on the reactions studied was a shorten-ing of the reaction times and a smooth increase in the yields. The subsequent reactions ofthe product with some nucleophiles are discussed. The structure of the products was provenby elemental analysis, IR and NMR spectra.Keywords: Creatinine, thiohydantoin, rhodanine, carbamoic acids, guanidine derivatives,Diels - Alder reaction, IR,

Benzothiazole Derivatives. 48. Synthesis of 3-Alkoxycarbonylmethyl-6-bromo-2-benzothiazolones and 3-Alkoxycarbonylmethyl-6-nitro-2-benzothiazolones as Potential Plant Growth Regulators

Department of Organic Chemistry, Faculty of Natural Sciences, Comenius University, Mlynska Dolina,SK - 842 15 Bratislava, Slovakia.*Author to whom correspondence should be addressed.Received: 17 March 1998 / Accepted: 8 March 1999 / Published: 26 March 1999Abstract: 3-Alkoxycarbonylmethyl-6-bromo- and 3-alkoxycarbonylmethyl-6-nitro-2-benzo-thiazolones were synthesized by reaction of alkylesters of halogenoacetic acids with 6-bromo-2-benzothiazolones and 6-nitro-2-benzothiazolones respectively. The compoundswere tested for plant growth stimulating activity on wheat ( Triticum aestivum ). The bromoderivatives manifested 25.4 % average stimulating activity in comparison with the control.The stimulation activity of the nitro derivatives was not significant. Optimal structures of thecompounds were obtained by a MMPI method, atomic charges and dipole moments werecalculated by a semiempirical AM1 method. On the basis of molecular electrostatic potentialit has been found that the biological activity of synthesized compounds depends on chargedistribution in the molecules.Keywords: 3-Alkoxycarbonylmethyl-6-bromo-2-benzothiazolones, 3-alkoxycarbonyl-methyl-6-nitro-2-benzothiazolones, plant growth regulators, AM1 calculations, lipophilicity.

Synthesis and Reactions of New 4-Oxo-4H-benzopyran-3-carboxaldehydes Containing Hydroxy Groups or 2-Oxopyran Cycles

The synthesis of eight hydroxy- and 2-oxopyranochromone-3-carboxaldehydes 3, 5 and their reactions with 2-hydroxyaniline, 2,4-dinitrophenylhydrazine and 2-benzothiazolylhydrazine were investigated. Products were confirmed by IR, NMR spectral and elemental analysis data. The semi-empirical AM1 quantum-chemical method has been used to study optimal geometries and heats of formation of synthesized 3-formylchromones.

3-(2-Alkylsulfanyl-6-benzothiazolylaminomethyl)-2-benzoxazolethiones - Synthesis and Photosynthesis-Inhibiting Activity in Spinach Chloropasts

Eva Sidoova, Katarina Kralova and Dusan Loos*Institute of Chemistry, Faculty of Natural Sciences, Comenius University, Mlynska dolina CH-2, SK-842 15 Bratislava, Slovakia. Tel. +421 7 60296342, Fax +421 7 65429064, E-mail loos@fns.uniba.sk*Author to whom correspondence should be addressed.Received: 12 May 1998 / Accepted: 5 March 1999 / Published: 29 March 1999Abstract: The synthesis and photosynthesis-inhibiting activity of 14 new 3-(2-alkylsulfanyl-6-benzothiazolylaminomethyl)-2-benzoxazolethiones are reported. The new compounds wereprepared by the reaction of 2-alkylsulfanyl-6-aminobenzothiazoles with 3-hydroxymethyl-2-benzoxazolethione. The structures of the compounds were verified by

Evaluation of Effect of Microwave Irradiation on Syntheses and Reactions of Some New 3-Acyl-methylchromones

The 3-Acyl-2-R-methylchromones (R = H, ArO, C6H4(CO)2N) were prepared in good yields by different methods from 2-hydroxyaroylacetone derivatives. Some subsequent reactions of these compounds with hydroxylamine and 3-formylchromones are described. The effect of microwave irradation on some condensation reactions was studied.

Synthesis of 2-(6-Acetamidobenzothiazolethio)acetic Acid Esters as Photosynthesis Inhibitors

The synthesis and photosynthesis-inhibiting activity of 13 new 2-(6-acetamidobenzothiazolethio)acetic acid esters are reported. The new compounds were prepared by acetylation of 2-(alkoxycarbonylmethylthio)-6-aminobenzothiazoles with acetic anhydride. The structure of the compounds was verified by 1H NMR spectra. The compounds inhibit photosynthetic electron transfer in spinach chloroplasts. The structure - activity relation was studied. Lipophilicity was found to influence substantially photosynthetic electron transfer.

Characterization of electronic properties of the Cr(CO)3 group in chromium, tricarbonyl [3-[(η6-aryl)methylene]-Z-1(3H)-isobenzofuranones] using spectral and theoretical methods

Abstract The IR, 13C- and 17O-NMR spectral characteristics of the Cr(CO)3 group in a series of eight chromium, tricarbonyl[3-[(η6-aryl)methylene]-Z-1(3H)-isobenzofuranones] were correlated mutually as well as with theoretical data obtained by optimized MMX force-field and EHT calculations. The net charges on the carbon and oxygen atoms of the CO group and their differences were found as the most appropriate quantitative characteristics for the electronic properties of the Cr(CO)3 group. Using the results of the previously reported linear correlations, the electron-withdrawing effect of the PhCr(CO)3 moiety, weakened by the back-donation effect, was estimated as σα≅0.45 on the scale of Hammett substituent constants.

Infrared spectra ofortho-substituted acetanilides: Vicinal effects and conformation

SummaryThe infrared spectra of twenty-twoortho-substituted acetanilides (1a–1v) in CCl4 and CHCl3 were measured in the region of the C=O and NH stretching vibrations and compared with those ofpara-substituted acetanilides (2a–2i). The wave numbers of the C=O stretching vibrations were analyzed using empirical substituent constants and single- and multiparametric correlations. On the basis of the above approaches, the separation of the polar effects into inductive, field, resonance, and steric components has been assessed for theortho-substituted series. For compounds containing polar substituents with double bonds, specific vicinal effects caused by intramolecular hydrogen bonding have been observed. The conformations ofortho-substituted acetanilides1a–1v were studied by both infrared spectroscopy and AM1 calculations.ZusammenfassungDie Infrarotspektren von 22ortho-substituierten Acetaniliden (1a–1v) in CCl4 und CHCl3 wurden im Bereich der C=O- und NH-Streckschwingungen gemessen und mit jenen vonpara-substituierten Acetaniliden (2a–2i) verglichen. Die Wellenzahlen der C=O-Streckschwingungen wurden mit Hilfe empirischer Substituentenkonstanten und ein- und mehrparametriger Korrelationen untersucht. Auf dieser Grundlage konnte für dieortho-substituierte Reihe eine Zerlegung der polaren Effekte in induktive, feldbedingte, resonanzabhängige und sterische Komponenten erzielt werden. In Verbindungen mit Doppelbindungen enthaltenden polaren Substituenten wurden durch intramolekulare Wasserstoffbrückenbindungen hervorgerufene spezifische Nachbargruppeneffekte beobachtet. Die Konformationen derortho-substituierten Acetanilide1a–1v wurden sowohl infrarotspektroskopisch als auch mittels AM1-Rechnungen untersucht.

Theoretical interpretation of infrared spectra of N-cyclohexyl-2-pyrrolidone in mixtures of hexane and CDCl3

SummaryThe infrared spectra of N-cyclohexyl-2-pyrrolidone (NCP) in binary mixtures of hexane and CDCl3 were interpreted theoretically in the region of C=O stretching vibrations using the AM1 semiempirical method. The results were compared with those obtained for N,N-dimethylacetamide (DMA), cyclohexanone (CX) and propanone (PR). Good correlations were found between the carbonyl stretching frequencies and the theoretical parameters of free and solvated species in equilibria with hexane-CDCl3 solvent mixtures.ZusammenfassungEs wurden die Infrarot-Spektren von N-Cyclohexyl-2-pyrrolidon (NCP) in binären Mischungen von Hexan und CDCl3 im Bereich der C=O Streckschwingung unter Benutzung der semiempirischen AM1-Methode interpretiert. Die Ergebnisse wurden mit denen für N,N-Dimethylacetamid (DMA), Cyclohexanon (CX) und Propanon (PR) verglichen. Es wurde eine gute Korrelation zwischen den Frequenzen der Carbonyl-Streckschwingung und den theoretischen Parametern der freien und solvatisierten Spezies im Gleichgewicht mit den Hexan-CDCl3 Lösungsmittelgemischen gefunden.

Structure elucidation of acetylation products of 2-acyl-1,3-indanediones by correlation of infrared spectral data

Summary2-(1-Acetoxyalkylidene)- and 2-(1-acetoxybenzylidene)-1,3-indanediones (1a–1e) were proven to be the products of acetylation of 2-acyl-1,3-indanediones (2a–2e) by ketene using a detailed investigation and correlation analysis of infrared spectral data as well as1H-NMR and13C-NMR spectra. Study by means of CNDO/2 and MMPI methods also demonstrates that the structure1 is more stable as the alternative one of 2-acyl-3-acetoxy-2-indene-1-ones (5). It was shown that the recently proposed general correlations v(C=O)s vs. v(C=O)as and v(C=O) vs. ∑X+(R) as well as the mechanical anharmonicities of asymmetric C=O stretching vibration can be successfully used as a tool of structural diagnostics of cyclic 1,3-dicarbonyl compounds.Zusammenfassung2-(1-Acetoxyalkyliden)- und 2-(1-Acetoxybenzyliden)-1,3-indandione (1a–1e) wurden mittels einer detaillierten infrarot-spektroskopischen Untersuchung (IR-Korrelation) und1H-NMR und13C-NMR Spektroskopie als Acetylierungsprodukte von 2-Acyl-1,3-indandionen (2a–2e) mit Keten nachgewiesen. CNDO/2- und MMPI-Rechnungen zeigten auch, daß Struktur1 stabiler ist, als die der alternativen 2-Acyl-3-acetoxy-2-inden-1-one5. Es wird gezeigt, daß die kürzlich vorgeschlagenen allgemeinen Korrelationen v(C=O)s gengen v(C=O)as und v(C=O) gegen ∑X+(R) und auch die mechanischen Anharmonizitäten der asymmetrischen C=O Streckschwingung erfolgreich als Werkzeug zur Strukturaufklärung cyclischer 1,3-Dicarbonyl-Verbindungen eingesetzt werden können.