Selenophene chemistry

Condensation of selenophene series-diketones containing selenienyl-2 or selenienyl-3 groups with malonyl dichloride gives isomeric- and -hydroxypyrones viz. 5-acyl-6- (selenienyl-2- or -3-) pyran-2,4-diones, separated chromatographically. Alkylation of the individual- and-hydroxypyrones with diazomethane gives in each case mixtures of- and-methoxy pyrones with the form predominating. The action of ammonium acetate on 5-acyl-6-(selenienyl-2- or -3-) hydroxypyrones lead to pyrone ring opening and formation of amides of disubstituted acetoacetic acids.For Part LVII see [12].     

Thermal reaction of hydrogen–butene-2-cis mixtures at 500°C: Hydrogenation,hydrogenolysis, and thermal reaction of the olefin

The thermal reaction of hydrogen–butene-2-cis mixtures has been studied in a static system at low extent of reaction around 500°C. Hydrogen does not affect the thermal reaction itself of the olefin, but gives rise to new stoichiometries of hydrogenolysis and hydrogenation, which are specified: The reaction is described in terms of a molecular and free-radical mechanism. It is shown that the key process for the hydrogenolysis–hydrogenation reaction is (1) and that the rate constant of this process can be determined from either propylene, or methane, or butene-1 formations: with θ = 4.57 × 10^?3 T kcal/mol. Other rate constants are estimated and agree with literature data.     

The case of triethylammonium cation loss during purification of certain nucleotide analogues: a cautionary note

Nucleotides, their analogues, and other phosphate esters and phosphoramidates often contain the triethylammonium cation as a counterion. We found that this may be lost during chromatographic purification or concentration of solutions, yielding products in acidic forms or containing sub-stoichiometric amounts of the counterion. This in turn may be detrimental, e.g., due to possible decomposition of a compound or inaccurate sample preparation. Correlations between the structure of studied compounds and their susceptibility for cation loss were analyzed. Modifications in preparative techniques were developed to obtain the studied compounds with stoichiometric anion to cation ratios.

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Graphical Abstract Triethylammonium salts of phosphate esters and phosphoramidates may lose the cationic component during chromatography or evaporation of solvent

     

Cobalt(II) and nickel(II) chloride complexes with some 2-(4′-Methyl-2′-pyridyl and 2′- or 8′-quinolyl)benz-X-azoles

Summary Complexes of general formula ML_mCl₂ · nH₂O, where M=cobalt(II) or nickel(II); L=2-(4-methyl, 2-pyridyl)-benzimidazole (mpbi), 2-(4-methyl, 2-pyridyl)benzothiazole (mpbt), 2-(4-methyl, 2-pyridyl)benzoxazole (mpbo), 2-(4-methyl, 2-quinolyl)benzoxazole (mqbo), or 2-(4-methyl, 8-quinolyl)benzoxazole (mqbo); m=1,2; n=0–3, were prepared and characterized by t.g.a., conductance and magnetic measurements, i.r. and diffuse-reflectance electronic spectra.All the ligands behave as bidentate and coordinate through the pyridine- and isoxazole-nitrogen atoms.The nickel complexes have distorted octahedral or fivecoordinate structures. The cobalt complexes arepseudo-tet- rahedral except Co(mpbo)₂Cl₂·2H₂O where the metal is six-coordinate.     

Über Heterocyclen, 15. Mitt.

Zusammenfassung Bei der Umsetzung von Vinylphenylketonen mit Harnstoffen oder Thioharnstoffen entstehen 2-Oxo- bzw. 2-Thionotetrahydropyrimidine und 2-Oxo- bzw. 2-Thiono-5-(-benzoyläthyl)-6-phenyltetrahydropyrimidine; -Benzoyläthyldimethylamin und analoge Basen geben mit Thioharnstoffen nur 5--Benzoyläthylderivate. 2-Oxo- und 2-Thiono-6-phenyltetrahydropyrimidine sind in der Kernstelle 5 alkylierbar brw. aminoalkylierbar.

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Vinyl phenyl ketones react with ureas or thioureas to 2-oxo-or 2-thionotetrahydropyrimidines and 2-oxo- or 2-thiono-5-(-benzoylethyl)-6-phenyltetrahydropyrimidines; -benzoylethyldimethylamines and analogous compounds give with thiocarbamides 5--benzoylethyl derivates. 2-oxo- and 2-thiono-6-phenyltetrahydropyrimidines react with 1-phenyl-2-propene-1-ones, -benzoylethylamines resp. formaldehyde and amines to 5-alkyl products.

     

Synthesis of cyanamides containing the phenothiazine fragment and their reactions with dialkyldithiophosphoric acids

Reaction of phenothiazine with dialkoxyphosphoryl or chlorosulfenyl isocyanide dichlorides has given 10-cyanophenothiazine, which adds dialkyldithiophosphoric acids at the CN bond. The addition products rearrange to 10-[N-(dialkoxythiophosphoryl) thiocarbamoyl]phenothiazines, which are prone to decompose to dialkoxythiophosphoryl isothiocyanates and phenothiazine, or on treatment with alkyl halides in the presence of base afford stable S-alkyl-N- dialkoxythiophosphoryl (l0-phenothiazinyl)isothioformamides. The reaction between 10-cyanophenothiazine and an excess of dithiophosphoric acids also affords 10-thiocarbamoylphenothiazine and tetraalkyl trithiopyrophosphates. An x-ray diffraction examination of the molecular structure of S-methyl-N-diisopropoxythiophosphoryl-(10-phenothiazinyl)isothioformamide has shown it to possess the Z-configuration. The dihedral angle formed by the benzene rings of the phenothiazine fragment is 125.7°. The products of the addition of dithiophosphoric acids to the CN bond of N,N-bis[2-(10-phenothiazinyl)-2-oxoethyl]cyanamide, obtained from 10-(chloroacety) phenothiazine and NaNHCN, also isomerize by 1,3S N migration of the thiophosphoryl group. Subsequent heterocyclization, with elimination of phenothiazine, affords 2-(dialkoxythiophosphorylimino)-3-[2-(10-phenothiazinyl)-2-oxoethyl]thiazolidin-5-ones.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 451–460, February, 1991.     

Atomic integrals containing rrr with λ, μ, ν ≥ −2

In this paper, the efficient evaluation of the atomic integrals I =∫rrrrrre^{?αr1?βr2?γr3}dτ with one or two factors r is described. These integrals are necessary for a lower-bound calculation for Li-like systems using the method of variance minimization or Temple's formula. © 1993 John Wiley & Sons, Inc.     

Synthesis of 3-phenyl- and 3-phenyl-1-methylimidazo [5, 1-b] benzoxazoles

Reduction of 2-benzoylbenzoxazole oxime gives 2-(-aminobenzyl) benzoxazole, converted to the formyl or acetyl derivative by treatment with, respectively, ethyl formate or acetic anhydride. Thiourea derivatives are obtained by treating 2-(-aminobenzyl) benzoxazole with arylisothiocyanates. Heating the above formyl or acetyl derivative with phosphorus oxychloride converts them to 3-phenyl- and 3-phenyl-1-methylimidazo [5, 1-b]-benzoxazole, which are representative members of a new tricyclic system. It did not prove possible to cyclize 1-[-(benzoxazolyl-2) benzyl]-3-phenylthiourea.     

New stable, isolable triarylmethyl based dyes absorbing in the near infrared

A series of new intensely coloured multicharged methylium compounds containing the 4-[2-ferrocenylethenyl]phenyl group and with significant electronic absorption in the near infrared have been prepared via acidification of the tertiary carbinols obtained by reaction of 4-[FcCHCH]C₆H₄Li with diethyl isophthalate, diethyl terephthalate, diethyl phthalate or the triethyl ester of 1,3,5-benzene carboxylic acid. Even more stable dyes were prepared from two new triarylmethanol derivatives containing 2,6-dimethoxy-4-[2-(ferrocenyl)ethenyl]phenyl or 2,6-dimethoxy-4-[2-[4-(dimethylamino)phenyl]ethenyl]phenyl groups which were prepared by reaction of 4-[FcCHCH]-2,6-MeO₂C₆H₂Li or 4-[4-Me₂NC₆H₄CHCH]-2,6-MeO₂C₆H₂Li (Fc = ferrocenyl) with diethyl carbonate. These carbinols on treatment with acid deposit dark-purple crystals which have been isolated and characterised spectroscopically. They absorb in the near infrared and, whereas their solutions begin to decolourise only after several days, they display long-term stability to air and moisture in the solid state.     

Synthesis of 2-[β-(5′-halogenofur-2′-yl)vikyl]benzimidazoles

2-[-(5-halogenofur-2-yl)vinyl]benzimidazoles (I) have been synthesized by the condensation of o-phenylenediamine with 5-halogeno-fur-2-ylacroleins or of 2-methylbenzimidazole with 5-halogenofurfurals. The methiodides of the 1-methyl-substituted derivatives ofI readily react with secondary amines (piperidine, dimethylamine)giving methiodides of 2-[-(5-dialkylaminofur-2-yl)vinyl]-1-methylbenzimidazoles.     

Podand-porphyrins with peripheral chelates

Alkylation of 5-(3-nitro-4-hydroxyphenyl)-10,15,20-triphenylporphyrin with chloropyridines[2,6-dichloromethyl-and 2-chloromethyl-6-(2-nitrophenoxymethylpyridine)] as well as condensation by a mixed-aldehyde method starting with formylpyridines [2-(2-nitro-4-formylphenoxymethyl)-6-(2-nitrophenoxy-methyl-) or 2,6-di(2-nitro-4-formylphenoxymethyl)pyridine], benzaldehyde, and pyrrole are used to synthesize previously unknown podand-porphyrins containing from one to four peripheral chelates.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 475–481, April, 1991.     

Alkyl-substituted dipyrrylmethenes and their oxa- and thia-analogs: “structure—solvation properties” correlations

New data on the spectral properties and solution enthalpies of unsymmetrically substituted 2-(alkyl-2-pyrrolylmethylidene)methylpyrrolium bromides (or ,-dipyrrylmethene hydrobromides), their ,-, ,-isomers, as well as their oxa and thia analogs, that is, 2-(2-furylmethylidene)- and 2-(2-thienylmethylidene)-3,4,5-trimethyl-1H-pyrrolium bromides, in solutions of organic solvents of different nature are presented. A decrease in the number of substituents, as well as replacement of the heteroatom (N) in one five-membered ring of the dipyrrylmetnehe by oxygen or sulfur atoms cause a monotonic hypsochromic shift of absorption bands in the electronic absorption spectrum and weakening of the chromophore properties of the compounds. The chromophore properties of isomers are weakened from the ,- to ,- and ,-dipyrrylmethenes. Main trends in the influence of structural factors on the specific features of thermooxidative destruction of the above-mentioned compounds were analyzed.     

Reaction of dimethylaminomethylenemalonaldehyde bis-N,O-acetal with ketones. A novel route to N-methylpyrroles

Condensation of the bis-N,O-acetal of amethylarrtinomethylenerrzalonaldehyde with ketones, -dimethylaminovinylketones, and -dimethylaminodienones is accompanied by an unusual intramolecular cyclization to give cross conjugated cyclic or acylic ketones containing an N-methyl pyrrole ring in the - or - and'-positions. This is a novel route to substituted pyrroles. Treatment of the bis-N,O-acetal of dimethylaminomethylenemalonaldehyde with 2-(3'-dimethylaminopropen-2'-ylidene)cyclopentanone gave a polyenyl tris-dimethylaminodiketone.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, Moscow 117913. Translated from Khimiya Geterotsiklicheskikh Soednenii, No.5, pp. 654–662, May, 1996. Original article submitted February 14, 1996.     

Studies on the resorcylates: biomimetic total syntheses of (+)-montagnetol and (+)-erythrin

6-(2,4-Dioxopentyl)-2,2-trimethyl-4H-1,3-dioxin-4-one on reflux in toluene gave MeCOCH₂COCH₂COCHCO, which cyclized to 6-(2-oxopropyl)-4-hydroxy-2H-pyran-2-one or was trapped with alcohols to produce resorcylate esters. The method was used for the synthesis of both enantiomers of montagnetol and erythrin.     

Charge Dispersal in the Quinuclidine Radical Cation and in the Quinuclidinium Ion,as Revealed by PE and ICR Spectroscopy

The n ionization energies I and the gas-phase basicities GB of CH₃-, Cl-, or CN-substituted quinuclidines have been measured by PE and ICR spectroscopy. The dependence of the shifts ΔI and ΔGB (relative to the values of the parent molecule) allow conclusions about the charge dispersal accompanying the n ionization or the protonation of quinuclidine in the gas phase. The agreement with the results of a minimal basis set ab initio calculation is excellent. Comparison of the solution pK_a values with either I or GB reveals that 2-substituted quinuclidines exhibit sizeable solvent-induced proximity effects, i.e. that the corresponding quinuclidinium ions are more acidic in solution than expected on the basis of the gas-phase basicities. This agrees with earlier results concerning 2-substituted pyridines.     

Metal oxide nanoparticles in electrochemical sensing and biosensing: a review

This review (with (318) refs) describes progress made in the design and synthesis of morphologically different metal oxide nanoparticles made from iron, manganese, titanium, copper, zinc, zirconium, cobalt, nickel, tungsten, silver, and vanadium. It also covers respective composites and their function and application in the field of electrochemical and photoelectrochemical sensing of chemical and biochemical species. The proper incorporation of chemical functionalities into these nanomaterials warrants effective detection of target molecules including DNA hybridization and sensing of DNA or the formation of antigen/antibody complexes. Significant data are summarized in tables. The review concludes with a discussion or current challenge and future perspectives.

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Graphical abstract ?

     

Unexpectedly rapid vapor-phase reaction between bromine and methyl iodide

The overall reaction (1) occurs readily in the gas phase, even at room temperature in the dark. The reaction is much faster than the corresponding process and does not involve the normal bromination mechanism for gas phase reactions. Reaction (1) is probably heterogeneous although other mechanisms cannot be excluded. The overall reactions (1) (2) proceed, for all practical purposes, completely to the right-hand side in the vapor phase. The expected mechanism is (3) (4) (5) (6) (7) where reaction (3) is initiated thermally or photochemically. Reaction (4) is of interest because little kinetic data are available on reactions involving abstraction of halogen by halogen and also because an accurate determination of the activation energy E₄ would prmit us to calculate an acccurate value of the bond dissociation energy D(CH₃? I).     

Ionic Hydrogenation of α,β-Unsaturated Ketones with Cyclohexane in the Presence of Aluminum Halides

4-Methyl-3-penten-2-one, 3-hepten-2-one, 3-methyl-1-phenyl-2-buten-1-one, 4-(2,4-dichlorophenyl)-, 4-(4-hydroxyphenyl)-, 4-(4-methoxyphenyl)-, 4-(2-hydroxyphenyl)-, and 4-(4-dimethylaminophenyl)-3-buten-2-ones, and 3-(4-methoxyphenyl)-1-phenyl-2-propenone react with cyclohexane in the presence of excess aluminum chloride or aluminum bromide in CH2Cl2 or CH2Br2, respectively, at room temperature to form the corresponding saturated ketones in high yields. Using 4-phenyl- and 4-(4-methoxyphenyl)-3-buten-2-ones as examples, it was shown that the reaction pattern does not change in going from the Lewis acids AlCl3 and AlBr3 to proton-donor acid system CF₃SO₃H-SbF₅. The reactive intermediates are likely to be C-protonated complexes of ,-unsaturated ketones with aluminum halides or their O,C-diprotonated analogs.     

Synthesis of 2-functionally substituted oxazolines and oxazolidines from methyl bromopropiolate and Β-amino alcohols

The reaction of methyl bromopropiolate with -amino alcohols containing a primary amino group generally results in the formation of 2-(methoxycarbonylmethyl)-²-1,3-oxazolines, while in the reaction with N-methyl- and N,N-dimethyl-substituted -aminoalcohols, 2-(methoxycarbonylmethylene)-1,3-oxazolidines, or their salts are formed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 406–409, March, 1991.