Display options:
Normal
Show Abstracts
Compact
Displaying article 1-22
p. 318-320
Received: 15 January 2005 / Published: 28 February 2005
Show/Hide Abstract
| Download PDF Full-text (23 KB) Abstract: n/a
p. 321-326
Received: 8 October 2004; in revised form: 4 November 2004 / Accepted: 10 November 2004 / Published: 28 February 2005
Show/Hide Abstract
| Download PDF Full-text (103 KB) Abstract: The 3 2 cycloaddition reaction of 1-(4-phenylphenacyl)-1,10-phenanthrolinium ylide with activated alkynes gave pyrrolo[1,2- 4a][1,10]phenanthrolines 6a-d. The "one pot" synthesis of 6a,b,d from 4, activatedalkenes, Et3 N and tetrakis-pyridine cobalt (II) dichromate (TPCD) is described. Thehelical chirality of pyrrolophenanthrolines 6b-d was put in evidence by NMRspectroscopy.
p. 327-333
Received: 29 October 2004 / Accepted: 16 December 2004 / Published: 28 February 2005
Show/Hide Abstract
| Download PDF Full-text (52 KB) Abstract: 3-Alkyl-thiazolo[3,2-a]benzimidazole derivatives are obtained in high yieldsvia the corresponding 4-alkyl-N-3-(2-aminophenyl)-thiazoline-2-thiones which are easilyprepared from 1,2-diaminobenzene, CS2 and halogenoketones. This new route comparesadvantageously with the classical mercaptobenzimidazole routes in term of simplicity,isolated yields and availability of the starting materials.
p. 334-345
Received: 29 March 2004 / Accepted: 10 May 2004 / Published: 28 February 2005
Show/Hide Abstract
| Download PDF Full-text (151 KB) Abstract: Valence topological charge-transfer (CT) indices are applied to the calculationof dipole moments μ. The μ calculated by algebraic and vector semisums of the CTindices are defined. The model is generalized for molecules with heteroatoms andcorrected for sp3 -heteromolecules. The ability of the indices for the description of themolecular charge distribution is established by comparing them with μ of the valence-isoelectronic series of cyclopentadiene, benzene and styrene. Two CT indices, μvec (vector semisum of vertex-pair μ) and μvec V (valence μvec ) are proposed. The μvec Vbehaviour is intermediate between μvec and μexperiment . The correction is produced in thecorrect direction. The best results are obtained for the greatest group. Inclusion of theheteroatom in the π-electron system is beneficial for the description of μ, owing to eitherthe role of additional p and/or d orbitals provided by the heteroatom or the role of stericfactors in the π-electron conjugation. The steric effect is almost constant along the seriesand the dominating effect is electronic. Inclusion of the heteroatom enhances μ, whichcan improve the solubility of the molecule. For heteroatoms in the same group, the ringsize and the degree of ring flattering are inversely proportional to their electronegativity.
p. 346-359
Received: 29 November 2004 / Accepted: 16 December 2004 / Published: 28 February 2005
Show/Hide Abstract
| Download PDF Full-text (133 KB) Abstract: A series of monosubstituted acetonitriles were treated with disulfur dichloride atroom temperature in CH2 Cl2 to afford 5-substituted-4-chloro-1,2,3-dithiazolium chlorides 1.Where the 5-substituent was not a good leaving group the chloride salts were converted intothe corresponding perchlorate salts 2 which were sufficiently stable and soluble to provideboth 1 H- and 13 C-NMR and cyclic voltammetry data. Several of the dithiazolium chlorideswere converted into their corresponding 4-substituted-3-chloro-1,2,5-thiadiazoles 13 ontreatment with aqueous ammonia. Mechanisms for all reactions are proposed.
p. 360-366
Received: 26 November 2004 / Accepted: 16 December 2004 / Published: 28 February 2005
Show/Hide Abstract
| Download PDF Full-text (157 KB) Abstract: The synthesis, characterization and X-ray crystal structure of 2-(4-chloro-phenyl)-7-methylpyrrolo[1,2-b]pyridazine are reported. The compound crystallizes in thespace group P21 /c (No.14) with a =3.8568(1), b = 11.0690(3), c = 26.4243(7) å, β =92.777(1)° and Z = 4. Accurate molecular parameters for the novel heterocyclic systemwere obtained from intensity data collected at 113K. The molecule assumes a planarconformation in the crystal and the packing is based on π-π stacking with interplanarspacing 3.400 å, typical of aromatic molecules with potential for displaying usefuloptical properties.
p. 367-375
Received: 23 November 2004 / Accepted: 16 December 2005 / Published: 28 February 2005
Show/Hide Abstract
| Download PDF Full-text (57 KB) Abstract: A route to methyl pyrrolo[2,3-d][1,2,3]thiadiazole-6-carboxylates as potential plant activators and inducers of systemic acquired resistance (SAR) is reported. A synthetic strategy based on cyclization of the thiadiazole ring system utilizing thionyl chloride via the Hurd-Mori protocol as key step was developed. Success of the ring closure reaction turned out to be highly dependent on the nature of the N-protecting group of the pyrrolidine precursor. While electron donors such as alkyl gave only poor conversion to the required 1,2,3-thiadiazoles, an electron withdrawing substituent such as methyl carbamate gave superior yields.
p. 376-382
Received: 12 July 2004 / Accepted: 1 September 2004 / Published: 28 February 2005
Show/Hide Abstract
| Download PDF Full-text (178 KB) Abstract: Iminoester hydrochlorides 1 have been synthesized. These compounds werethen converted into ester ethoxycarbonyl hydrazones 2, from which in turn a new seriesof substituted 4-amino-4,5-dihydro-1H-1,2,4-triazole-5-ones, 3, was then prepared.Finally a set of isatin imine derivatives 4 was obtained from the reaction of compounds 3with isatin. The structures of all the new synthesized compounds were confirmed byelemental analyses, IR, 1 H-NMR and 13 C-NMR spectra.
p. 383-393
Received: 12 November 2004; in revised form: 18 November 2004 / Accepted: 19 November 2004 / Published: 28 February 2005
Show/Hide Abstract
| Download PDF Full-text (144 KB) Abstract: A method to synthesize 2-phenylselenenyl-1,3-anti-diols and 2-phenyl- selenenyl-1,3-anti-azidoalcohols via hydroxy- or azido-selenenylation of trans-allylic alcohols is reported. Moreover, the first example of hydroxyl-selenenylation of an allylic azide is presented. Yields ranging from moderate to good and diastereomeric ratios up to 95:5 are achieved.
p. 394-400
Received: 8 November 2004; in revised form: 28 January 2005 / Accepted: 29 January 2005 / Published: 28 February 2005
Show/Hide Abstract
| Download PDF Full-text (172 KB) Abstract: Benzene, halobenzenes, and a number of more or less deactivated arenes,including nitrobenzene, readily reacted in anhydrous HIO3 /AcOH/Ac2 o/conc. H2 SO4 mixtures to probably give ArIO2 intermediates or other hypervalent species (notisolated). The final reaction mixtures were poured into excess aq. Na2 SO3 solution (areductant) to give the purified iodinated products in 39-83% yields.
p. 401-406
Received: 8 November 2004; in revised form: 18 November 2004 / Accepted: 18 November 2004 / Published: 28 February 2005
Show/Hide Abstract
| Download PDF Full-text (162 KB) Abstract: A fast and simple method for the oxidative iodination of some activated arenes and heteroarenes, either under microwave irradiation or by conventional heating, is reported, using diiodine and ortho-periodic acid as the oxidant. The reactions were carried out in hot 95% ethanol under a reflux condenser. For the microwave assisted reactions, the reaction times were always notably shortened, but the yields were nearly the same as those afforded by the conventional method.
p. 407-416
Received: 17 February 2004; in revised form: 10 October 2004 / Accepted: 13 October 2004 / Published: 28 February 2005
Show/Hide Abstract
| Download PDF Full-text (85 KB) Abstract: A series of 1-aryl substituted dihydro-, 5-methyldihydro- and 6-methyl-dihydro-2,4(1H,3H)pyrimidinediones and their 2-thio analogues were obtained byreaction of the corresponding β-alanines or α-methyl- and β-methyl-β-alanines with ureaor potassium thiocyanate. The reaction of N-(2,3- and 3,5-dimethylphenyl)-α-methyl-β-alanines with ethyl acetoacetate gave 1-(2,3- or 3,5-dimethylphenyl)-2,5-dimethyl-1,4,5,6-tetrahydro-4(1H)pyridones. The combined spectral data obtained by 1 H-, 13 C-,1 H/13 C (HETCOR) NMR and IR provided useful information about the structure of theproducts synthesized in this work.
p. 417-426
Received: 2 April 2004; in revised form: 21 December 2004 / Accepted: 22 December 2004 / Published: 28 February 2005
Show/Hide Abstract
| Download PDF Full-text (186 KB) Abstract: The sequence specific recognitions between DNAs and proteins play important roles in many biological functions. The use of double-stranded DNA arrays (ds-DNA arrays) for studying sequence specific recognition between DNAs and proteins is a promising method. Here we report the use of a ds-DNA probe with multi operation sites of restriction proteins in the middle sequence to investigate DNA-protein sequence-specific interactions including methylation. We arranged EcoR I site and Rsa I site on the same duplex DNA probe to fabricate ds-DNA arrays. We used the ds-DNA arrays to study DNA-restriction enzyme reactions before and after duplex DNA methylation under different probe concentration and reaction time conditions. Our results indicated that the ds-DNA arrays can be further biochemically modified and made accessible for interactions between DNAs and proteins in complex multi-step gene-regulation processes.
p. 427-434
Received: 27 October 2004; in revised form: 18 January 2005 / Accepted: 20 January 2005 / Published: 28 February 2005
Show/Hide Abstract
| Download PDF Full-text (214 KB) Abstract: In the search for better herbicides a series of 1-alkyl-3-(α-hydroxy-(un)substituted benzylidene)pyrrolidine-2,4-diones were prepared and their structure-activity relationships studied. All their structures have been confirmed by 1 H-NMR andelemental analysis. The preliminary bioassay results indicated that some of them have highherbicidal activity against annual dicotyledonous and monocotyledonous plants.
p. 435-443
Received: 4 September 2004; in revised form: 28 December 2004 / Accepted: 30 December 2004 / Published: 28 February 2005
Show/Hide Abstract
| Download PDF Full-text (129 KB) Abstract: An analysis of the 1 H- and 13 C-NMR spectra of a series of 1,2-diaryl-1H-4,5-dihydroimidazoles and comparisons with 4,5-dihydroimidazoles having differentsubstitution patterns are presented. The influence of different 1-aryl and 2-aryl groupsubstituents on spectroscopic parameters of the heterocyclic ring and on the contributionsof possible mesomeric structures in the system was determined. Spectroscopic featuresare coherent with the presence of two conjugated systems (Ar1 -N and Ar2 -C=N) whichcompete with the delocalization characteristics of the amidine system.
p. 444-456
Received: 27 August 2004; in revised form: 23 December 2004 / Accepted: 24 December 2004 / Published: 28 February 2005
Show/Hide Abstract
| Download PDF Full-text (230 KB) Abstract: The parallel solution-phase synthesis of a new combinatorial library of 3-[4-(R1-coumarin-3-yl)-1,3-thiazol-2-ylcarbamoyl]propanoic acid amides 9 has been developed. The synthesis involves two steps: 1) the synthesis of core building blocks – 3- [4-(coumarin-3-yl)-1,3-thiazol-2-ylcarbamoyl]propanoic acids, 6 – by the reaction of 3-(ω-bromacetyl)coumarins 1 with 3-amino(thioxo)methylcarbamoylpropanoic acid (5); 2) the synthesis of the corresponding 3-[4-(coumarin-3-yl)-1,3-thiazol-2-yl- carbamoyl]propanoic acids amides 9 using 1,1’-carbonyldimidazole as a coupling reagent. The advantages of the method compared to existing ones are discussed.
p. 457-474
Received: 2 June 2004; in revised form: 12 December 2004 / Accepted: 15 December 2004 / Published: 28 February 2005
Show/Hide Abstract
| Download PDF Full-text (273 KB) Abstract: The solvent effect on the position of the carbonyl vibrational stretching ofacetylferrocene in aprotic media was studied in this work. The solvent-induced shifts in thisorganometallic compound were interpreted in terms of the alternative reaction field model(SCRF-MO) proposed by Kolling. In contrast to the established trends for carbonyl groupsin organic systems, the results suggest that the continuum models for the reaction field arenot adequate and that the influence of dipolarity-polarizability described by aninhomogeneous coupling function θ (ε ) L(n 2 ) that assumes optical dielectric saturation isresponsible for the carbonyl band shift and, there is empirical evidence that the effect offield-induced intermolecular interaction on band shift, interpreted in terms of the van derWaals forces from the solvent, have a important contribution to this phenomena.
p. 475-480
Received: 30 June 2004; in revised form: 15 July 2004 / Accepted: 1 August 2004 / Published: 28 February 2005
Show/Hide Abstract
| Download PDF Full-text (105 KB) Abstract: 5-Furan-2-yl[1,3,4]oxadiazole-2-thiol (Ia) and 5-furan-2-yl-4H-[1,2,4]-triazole-3-thiol (Ib) were synthesized from furan-2-carboxylic acid hydrazide. Mannich basesand methyl derivatives were then prepared. The structures of the synthesized compoundswere confirmed by elemental analyses, IR and 1 H-NMR spectra. Their thiol-thione tautomericequilibrium is described.
p. 481-487
Received: 2 July 2004; in revised form: 2 February 2005 / Accepted: 3 February 2005 / Published: 28 February 2005
Show/Hide Abstract
| Download PDF Full-text (52 KB) Abstract: Cinnamic acids have been prepared in moderate to high yields by a new direct synthesis using aromatic aldehydes and aliphatic carboxylic acids, in the presence of boron tribromide as reagent, 4-dimethylaminopyridine (4-DMAP) and pyridine (Py) as bases and N-methyl-2-pyrolidinone (NMP) as solvent, at reflux (180-190°C) for 8-12 hours.
p. 488-491
Received: 1 August 2004; in revised form: 27 December 2004 / Accepted: 29 December 2004 / Published: 28 February 2005
Show/Hide Abstract
| Download PDF Full-text (99 KB) Abstract: The development of a novel route for the synthesis of a new class of compounds is described. The first tripodal, tris-indole amines are prepared by straightforward routes.
p. 492-507
Received: 18 May 2004; in revised form: 28 December 2004 / Accepted: 29 November 2004 / Published: 28 February 2005
Show/Hide Abstract
| Download PDF Full-text (162 KB) Abstract: This review article discusses the reaction of nitrilimines and nitrile oxides with hydrazines, hydrazones, and oximes. Three reaction modes were observed. The article mainly covers our work published over the last fifteen years, in which interesting heterocyles such as oxadiazoles, triazoles, and tetrazines were synthesized and fully characterized.
p. 508-515
Received: 4 January 2005; in revised form: 9 February 2005 / Accepted: 10 February 2005 / Published: 28 February 2005
Show/Hide Abstract
| Download PDF Full-text (166 KB) Abstract: An efficient protocol for the amination of 6-chloropurine derivatives through nucleophilic aromatic substitution under microwave irradiation was developed and applied to the synthesis in two steps of a series of new acyclic nucleosides (acyclovir analogues) starting from commercially available compounds.
Displaying article 1-22
Plain Text
BibTeX
BibTeX (without abstracts)
Endnote
Endnote (without abstracts)
Tab-delimited
PubMed XML
DOAJ XML
AGRIS XML
to open them.