Synthesis of Novel 2-Aminothiophene-3-carboxylates by Variations of the Gewald Reaction

Summary.  The synthesis of the title compounds through variations of the Gewald reaction is presented. Knoevenagel condensation of methylketone derivatives with methyl cyanoacetate and subsequent treatment of the α,β-unsaturated nitriles with sulfur and amine resulted in the corresponding 2-aminothiophenes 5 or isomers 9 and 10. Reaction of methylketone derivatives bearing a leaving group at the methyl group under modified Gewald conditions selectively led to the formation of 4-substituted 2-aminothiophenes 9a and 12. The introduction of the sulfur atom occurs through nucleophilic displacement with sodium sulfide. Received July 5, 2000. Accepted (revised) August 23, 2000     

The Synthesis of New Phthalocyanines Substituted with 12-Membered Diazadioxa Macrocycles

Summary.  A macrocyclic diazadioxa dibromo compound was synthesized by ring closure of 1,2-bis-(2-iodoethoxy)-4,5-dibromo-benzene and 1,4-bis-(p-tolylsulfonyl)-ethylenediamine. Its phthalonitrile derivative was obtained by cyano substitution. This diazadioxa macrocyclic dibromo derivative was directly converted into the copper(II) phthalocyanine by reaction with CuCN in tetramethyl urea. Conversion of this phthalonitrile derivative into the metal-free phthalocyanine was accomplished by refluxing with DBU. The zinc(II) phthalocyanine was prepared by reaction of the dinitrile derivative with Zn(OAc)₂ in quinoline. The lutetium bis-(phthalocyaninate) complex was obtained by treating the dinitrile derivative with anhydrous lutetium acetate and DBU in 1-hexanol. The new compounds were characterized by elemental analyses and IR, ¹H NMR, mass, UV/Vis, and ESR spectra. Received May 8, 2001. Accepted (revised) June 25, 2001     

Determination of Thiosemicarbazones by Means of the Induced Iodine-Azide Reaction

 The iodine-azide reaction induced by eight thiosemicarbazones was investigated. Inducing properties of thiosemicarbazones are different and depend on the parent carbonyl compound used for synthesis. The inductor coefficients of the examined thiosemicarbazones vary from 61 to 176. Optimum conditions for the determination of microamounts of thiosemicarbazones are given. The detection limit for the determination by the back-titration method depends on the inducing activity and is 0.9 μg for phenyl-thiosemicarbazones and 2 μg for diethyl-thiosemicarbazone in a 5-mL sample, and this corresponds to a concentration of 0.9 × 10⁻⁶ mol/L and , respectively. The automatic titration with the diluted iodine solution decreases the detection limit to about 50 ng in a 10-mL sample. Received October 28, 1998. Revision April 9, 1999.     

Synthesis and Characterization of New Unsymmetrically Substituted Phthalocyanines

Summary.  Unsymmetric metallophthalocyanines (M=Zn, Co, Ni) carrying alkylthio and acetyloxyethylthio groups on peripheral positions were prepared from 4,5-bis-alkylthio-phthalonitrile, 4,5-bis-(acetyloxyethylthio)-phthalonitrile, and the corresponding anhydrous metal salts Zn(CH₃COO)₂, NiCl₂, and CoCl₂. The extremely soluble compounds were characterized by their IR, ¹H NMR, and UV/Vis spectra. Their long wavelength absorption band was found to be bathochromically shifted; their solubility is superior to that of symmetrical phthalocyanines. Received July 27, 1999. Accepted (revised) September 30, 1999     

Synthesis and Characterization of a New 2,2′-Azoquinoxaline and its Complexeswith Platinum and Palladium

Summary.  Platinum and palladium dichlorides react readily with 2,2′-azoquinoxaline to give the di-μ-chloro-2,2′-azobis-(7,7′-bis-benzoyl-quinoxaline) diplatinum(II) and dipalladium(II) complexes. These crystalline complexes exhibit both metal-carbon binding and coordinate metal-nitrogene binding to azoquinoxaline. Received July 16, 1999. Accepted (revised) October 22, 1999     

Synthesis of New Metal-Free and Metal-Containing Phthalocyanines with Tertiaryor Quaternary Aminoethyl Substituents

Summary.  A novel phthalodinitrile derivative carrying dimethylaminoethylsulfanyl groups at positions 4 and 5 was synthesized from 2-dimethylaminoethanethiol hydrochloride and 1,2-dichloro-4,5-dicyanobenzene. Its cyclotetramerization in the presence of 2-dimethylamino-ethanol or metal salts (CoCl₂, Zn(OAc)₂) gave metal-free or metal-containing phthalocyanines (M = Co or Zn). These phthalocyanines were converted into water soluble quaternized products by reaction with methyl iodide. The new compounds were characterized by elemental analysis, IR, NMR, and electronic spectra.     

Synthesis of New Functionalized Compounds Related to p-Extended Tetrathiafulvalenes with Quinonoidal Structures Bearing a Ferrocene Moiety

Summary.  A number of π-extended conjugated tetrathiafulvalene (TTF) analogues were synthesized as new π-donors, and their structures and physical properties were determined. UV/Vis spectra and cyclic voltammetry of the π-extended ferrocenyl donors were studied in comparison with ferrocene, ferrocenylquinone, and the parent donor. A three-electron redox behaviour was observed. The absorption spectrum of the new donor 16 showed a slight red-shift and a slight increase in intensity relative to the compared compounds. Received September 19, 2001. Accepted (revised) October 23, 2001     

Synthesis of 2H-Thiopyrans by Rhodium(II) Acetate-Catalyzed Reaction of 4-Amino-2,5-dihydro-3-thiophenecarbonitriles with a-Diazocarbonyl Compounds II [1]

Summary.  The reaction of 4-amino-2,5-dihydro-2- and -5-methyl-3-thiophenecarbonitriles with α-diazocarbonyl compounds in the presence of rhodium(II) acetate gave regioselectively 4-cyano-2H-thiopyrans (C₂-S insertion) in moderate to good yields; 5-cyano-2H-thiopyrans (C₅-S insertion) were not isolated. The starting compounds were synthesized by reaction of tetrahydro-2- and -5-methyl-4-oxo-3-thiophenecarbonitriles with morpholine, piperidine, and pyrrolidine in the presence of formic acid in ethanol. Received November 13, 2000. Accepted December 12, 2000     

On the Synthesis of 2-Acetyl-4-aryl-6H-1,3,4-thiadiazin-5-ones by Reaction of Nitrilimines with α-Mercapto Alkanoic Acids

Summary.  N′-Arylacetonitrilimines were generated from acetohydrazonyl chlorides and reacted with mercaptoalkanoic acids forming 4-aryl-5-oxo-3-thiahexanoic acids. These were cyclized by reaction with dicyclohexyl carbodiimide yielding 2-acetyl-4-aryl-6H-1,3,4-thiadiazin-5-ones. Received November 13, 2001. Accepted January 9, 2002     

Reaction of Some Alkenols with Tetrachloromethane

Summary.  The reaction of some alkenols with tetrachloromethane in the presence of a radical initiator was investigated. Regarding the effects of structural features of the starting alkenol (number and position of methyl substituents at the double bond and at the carbinol carbon atom, constitutional relationship between the double bond and the hydroxyl group) there are two possible competing reactions: addition and cyclization. In the case of the simplest alkenols (without substituents and with a more remote double bond) addition occurs; mono- and disubstituted secondary and tertiary Δ⁴- and Δ⁵-alkenols cyclize in high yields to give the corresponding cyclic ethers. Received March 17, 2000. Accepted (revised) May 31, 2000     

Nitrosation of Phenolic Compounds: Effects of Alkyl Substituents and Solvent

Summary.  Nitrosation reactions of phenol, o-cresol, 2,6-dimethylphenol, o-tert-butylphenol, 2-hydroxyacetophenone, and 2-allylphenol in water and water/acetonitrile were studied. Kinetic monitoring of the reactions was accomplished by spectrophotometric analysis of the nitrosated products at 345 nm. The dominant reaction was C-nitrosation via a mechanism consisting of an attack on the nitrosatable substrate by NO⁺/NO₂H₂ ⁺ followed by a slow proton transfer. The values of the rate constants of phenolic C-nitrosation were increased by electron donating substituents, and a good Hammett correlation was observed with ρ = −6.1. The results also revealed the strong effect of pH and the permitivity of the reaction medium on the rate constant, whose maximum values were observed for pH ≈ 3, decreasing strongly for higher pH values. The study in water/acetonitrile with up to 25% acetonitrile showed that it is possible to inhibit the reaction strongly by increasing the percentage of the organic component. The conclusions drawn show that (i) it is possible to predict the rate of nitrosation of phenolics as a function of the meta-substituents on the phenol ring and (ii) the nitrosation of phenolics can be strongly inhibited by increasing the pH of the reaction medium as well as by lowering its dielectric constant. Received July 13, 2001. Accepted (revised) September 18, 2001     

Replacement of Methoxy by tert-Butyl on a Naphthalene Residue: An Unexpected Reaction During a Snieckus ortho-Lithiation

Summary.  When 1-methoxy-2-naphthalene carboxylic acid diethylamide was reacted with tert-butyl lithium in presence of TMEDA and 3,5-dimethoxybenzaldehyde was subsequently added to the reaction mixture, (P, S/M, R)- and (P, R/M, S)-1-tert-butyl-3-((3,5-dimethoxyphenyl)-hydroxymethyl)-naphthalene-2-carboxylic acid diethylamide were formed instead of the corresponding 1-methoxy derivative. The diastereomeric relationship of the products is due to a sterically severely hindered rotation around the amide-aryl bond. Received May 11, 2001. Accepted May 18, 2001     

The Gould-Jacobs Reaction of5-Aminoquinoxaline

Summary.  Reaction of 5-aminoquinoxaline with alkoxymethylene derivatives affords the corresponding quinoxalinoaminoethylenes. These undergo a thermal cyclization to yield angularly annelated 10H-pyrido[2,3-f]quinoxalines. The structures of all products were deduced from their IR, UV, mass, ¹H, and ¹³C NMR spectra. Received September 24, 1999. Accepted November 18, 1999     

Microwave Activated Solid Support Synthesis of New Antibacterial Quinolones

Summary.  A novel synthesis of 6-fluoro-7-(5-aryl-1,3,4-thiadiazol/oxadiazol-2-yl-sulfanyl)-4-quinolone-3-carboxylic acids from 7-chloro-6-fluoro-4-quinolone-3-carboxylic acid and 5-substituted 1,3,4-thiadiazoles/oxadiazoles on basic alumina under microwave activation is described. All compounds were screened for their in vitro antibacterial activity against B. lichenformis, 2689, K. aerogens 2281, S. typhimurium 2501, E. herbicola 2491, and P. vulgaris 2027 and found to possess activities comparable to that of the standard drug norfloxacin. Received May 2, 2000. Accepted (revised) June 13, 2000     

Reaction of 3-Cyano-2-amino-4,5,6,7-tetrahydrobenzo[b]thiophene with Enaminonitriles

Summary.  2-Amino-3-cyano-4,5,6,7-tetrahydrobenzo[b]thiophene with ethyl β-amino-α-cyano-γ-ethoxycarbonylcrotenoate yields the corresponding amide derivative. That compound reacts with benzenediazonium chloride to give the phenyl hydrazone derivative. This type of compounds was cyclized to give pyridazine and pyridine derivatives, respectively. Chemical reactivities of the latter were studied to give fused heterocyclic compounds with antimicrobial activities. Corresponding author. E-mail: rmmohareb@hotmail.com Received February 8, 2002; accepted (revised) March 28, 2002     

Synthesis and Some Pharmacological Studies of New Benzenesulfonamide Derivatives

Summary.  New benzenesulfonamide derivatives containing pyrazole and oxadiazole moieties were prepared starting from sodium saccharin. The structures of the novel compounds were characterized by elemental analyses and spectroscopic methods. The new compounds are structurally related to the COX-2 inhibitor celecoxib (Celebrex^?). A pharmacological study of the pyrazoles revealed that several compounds possess higher analgesic and antiinflammatory activities than celecoxib, particularly 11 and 17. Most of the pyrazoles showed a significant increase in the sleeping time of thiopentone anaesthesized mice and also protected mice against the convulsive and lethal effects of pentylenetetrazole. Moreover, the ulcerogenic activity of those compounds showing a pronounced antiinflammatory effect was also studied. Received August 20, 2001. Accepted (revised) November 19, 2001     

Reaction of Triethyl Phosphite with Boron Tribromide

Summary.  Reaction of boron tribromide with triethyl phosphite led to the formation of triethyl tribromoborophosphate 1, a complex bearing a P→B bond. Received November 19, 1999. Accepted (revised) January 21, 2000     

Synthesis of 3-Diaminomethylene-2(3<Emphasis Type="BoldItalic">H</Emphasis>)-furanones by Reaction of 2-Amino-4,5-dihydro-3-furancarboxamides with Amines

Summary.  The reaction of 2-amino-4,5-dihydro-3-furancarboxamides with morpholine in the presence of acetic acid in pyridine or under the influence of ammonium acetate gave the corresponding 3-diaminomethylene-4,5-dihydro-2(3H )-furanones; 4,5-dihydro-2-morpholino-3-furancarboxamides were not isolated. One of the former reacted with benzylamine to give (E )- and (Z )-3-(amino-(benzylamino)-methylene)-4,5-dihydro-4-phenyl-2(3H )-furanones and 2-benzylamino-4,5-dihydro-4-phenyl-3-furancarboxamide. Received October 4, 2001. Accepted October 10, 2001     

Synthesis and Stereochemistry of Some New Spiro-1,3-perhydrooxazines

Summary.  The synthesis and the stereochemistry of new spiro-1,3-perhydrooxazines are reported. The stereoisomerism of these compounds is discussed considering the data of conformational analysis, the helical chirality of the spiro[5.5]undecane skeleton, and the triligand virtual chiral center belonging to the 1,3-perhydrooxazine ring. Received February 21, 2000. Accepted (revised) April 18, 2000