Kolbe-Schmitt reaction of sodium 2-naphthoxide

The mechanism of the Kolbe-Schmitt reaction of sodium 2-naphthoxide is examined by means of the B3LYP/LANL2DZ method. After the initial formation of sodium 2-naphthoxide-CO₂ complex, the carbon of the CO₂ moiety performs an electrophilic attack on the naphthalene ring. Further transformations lead to the formation of sodium 2-hydroxy-1-naphthoate. Sodium 3-hydroxy-2-naphthoate is formed by a 1,3-rearrangement of the CO₂Na group. Our findings are in good agreement with the experimental results on the carboxylation reaction of sodium 2-naphthoxide. Correspondence: Svetlana Marković, Faculty of Science, University of Kragujevac, 34000 Kragujevac, Serbia     

Formation of sodium 6-hydroxy-2-naphthoate in the Kolbe-Schmitt reaction

This work is an extension of our investigation of the mechanism of the Kolbe-Schmitt reaction of sodium 2-naphthoxide. The carboxylation reaction of sodium 2-naphthoxide in the position 6 is examined by means of the B3LYP/LANL2DZ method. After the initial formation of sodium 2-naphthoxide-CO₂ complex, the carbon of the CO₂ moiety performs an electrophilic attack on the naphthalene ring in position 8. Further transformations lead to the formation of sodium 6-hydroxy-2-naphthoate. Our findings are in good agreement with the experimental results on the carboxylation reaction of sodium 2-naphthoxide.     

Rapid SnCl<Subscript>2</Subscript> catalyzed phenylselenoetherification of (<Emphasis Type="Italic">Z</Emphasis>)- and (<Emphasis Type="Italic">E</Emphasis>)-hex-4-en-1-ols

A fast and efficient method for intramolecular heterocyclization of (Z)- and (E)-hex-4-en-1-ols was developed. The method does not cause side reactions of the substrates and provides the cyclic phenylselenoethers in high yields after only few minutes. A catalytic amount of SnCl₂ increased the yield, but in the presence of an equimolar amount of SnCl₂, formation of corresponding cyclic ethers were almost quantitative and reaction occurred instantaneously under extremely mild experimental conditions. Correspondence: Zorica M. Bugarčić, Department of Chemistry, Faculty of Science, University of Kragujevac, Radoja Domanovića 12, P.O.Box 60, YU-34000 Kragujevac, Serbia.     

Synthesis of Schiff bases and benzylamino derivatives containing [1-B<Subscript>10</Subscript>H<Subscript>9</Subscript>NH<Subscript>3</Subscript>]<Superscript>−</Superscript> anion

Reactions of an amino derivative of the closo-decaborate anion [1-B₁₀H₉NH₃]^– with aromatic aldehydes afforded Schiff bases [1-B₁₀H₉NH=CHAr]^– (Ar=Ph, C₆H₄-2-OMe, or C₆H₄-4-NHCOMe). The reduction of the latter with sodium borohydride gave the corresponding benzylamino derivatives [1-B₁₀H₉NH₂CH₂Ar]^–.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2004–2007, September, 2004.     

Natriumkomplexe mit Salicylideniminen: Synthesen,Strukturen, CO2‐Aufnahme und Carboxylierung von 2‐Fluorpropiophenon bzw. Estronmethylether

Chiral salicylidenphenethylamines (R)‐HA or (S)‐HA , 2‐salicylidenfurfuryl‐imines HB , and 2‐salicylidenaminoethanol HC react with sodium hydride or sodium hexamethyldisilylamide to form the sodium complexes [Na(R)‐A] ₄ · 0,5 Et ₂ , [Na(S)‐A] ₄ · 0,5 Et ₂ O (1) , [NaB] ₄ · 0,5 Ph‐Me (2) and [(dme)NaC] ₄ (3) . In the presence of 18‐crown‐6 the complex [Na(18‐crown‐6)(thf) ₂ ] ₂ [Na ₂ (C)] ₄ · THF (4) can also be isolated. The crystal structure analyses of both 1 and 2 show that heterocubane structures with a Na₄O₄ frame work are formed. Additionally, the imine nitrogen atom is bonded at the Na atom which has the coordination number 4 in 1 . Additional coordination of the furfuryl oxygen atom results in the coordination number five for the sodium atom in 2 . In 3 which is also a tetramer, two Na₂O₂ units are connected via two imino‐ethanol bridges Na(1)‐N(=CH‐phenolat)‐CH₂CH₂‐OH‐Na(2A). The crystal structure analysis displays that 4 is an ionic compound consisting of two [(thf)₂Na(18‐crown‐6)]⁺ cations and the dinuclear dianion [Na ₂ (C) ₄ ] ^2? . Both 1 and 2 are carboxylation reagents which transfer CO₂ to 2‐fluoropropiophenone. 1 is more active than 2 , but 3 and 4 are inactive.     

Michael reaction. IV. NaNH2 catalyzed one stage reaction between phenylacetic acid dialkylamides and cinnamic acid methyl ester or dialkylamides. Influence of reaction conditions on the stereochemistry

The NaNH₂ catalyzed one stage reaction between phenylacetic acid dialkylamides and cinnamic acid methyl ester or dialkylamides was studied under various conditions. Conditions were found for easy preparation of each of the both possible diastereomeric derivatives of 2,3-diphenylglutaric acid. It was proved that catalytic amounts of NaNH₂ take part in the reaction. It is assumed that the observederythro/threo equilibrium ratios are determined by an isomerization via two different carbanions (at C₂ and C₄) of the reaction products.Part III:J. Stefanovsky andL. Viteva, Comun. Dept. Chem. Bulg. Acad. Sci.4, 159 (1971).     

Synthesis of nanosized silicon particles by a rapid metathesis reaction

A solid-state rapid metathesis reaction was performed in a bed of sodium silicofluoride (Na₂SiF₆) and sodium azide (NaN₃) powders diluted with sodium fluoride (NaF), to produce silicon nanoparticles. After a local ignition of Na₂SiF₆+4NaN₃+kNaF mixture (here k is mole number of NaF), the reaction proceeded in a self-sustaining combustion mode developing high temperatures (950–1000 °C) on very short time scales (a few seconds). Silicon nanoparticles prepared by the combustion process was easily separated from the salt byproducts by simple washing with distilled water. The structural and morphological studies on the nanoparticles were carried out using X-ray diffractometer (XRD) and field emission scanning electron microscope (FESEM). The mean size of silicon particles calculated from the FESEM image was about 37.75 nm. FESEM analysis also shows that the final purified product contains a noticeable amount of silicon fibers, dendrites and blocks, along with nanoparticles. The mechanism of Si nanostructures formation is discussed and a simple model for interpretation of experimental results is proposed.     

Synthesis and ac susceptibility of YCa2Cu3O7−δ

The bulk superconducting YCa₂Cu₃O_7−δ compounds are prepared at an ordinary pressure of oxygen by conventional solid-state reaction method. The formation of sample is tested by means of XRD and is studied for their ac susceptibility below room temperature up to 77.5 K. The samples are found single-phase orthorhombic structure and found superconducting at 83.5 K. It is shown that the analysis is consistent with published data on YBa₂Cu₃O_7−δ oxide superconductor.     

Effect of sodium cation on the electrochemical reduction of CO<Subscript>2</Subscript> at a copper electrode in methanol

The electrochemical reduction of CO₂ with a Cu electrode in methanol was investigated with sodium hydroxide supporting salt. A divided H-type cell was employed; the supporting electrolytes were 80 mmol dm⁻³ sodium hydroxide in methanol (catholyte) and 300 mmol dm⁻³ potassium hydroxide in methanol (anolyte). The main products from CO₂ were methane, ethylene, carbon monoxide, and formic acid. The maximum current efficiency for hydrocarbons (methane and ethylene) was 80.6%, at −4.0 V vs Ag/AgCl, saturated KCl. The ratio of current efficiency for methane/ethylene, r _f(CH₄)/r _f(C₂H₄), was similar to those obtained in LiOH/methanol-based electrolyte and larger relative to those in methanol using KOH, RbOH, and CsOH supporting salts. In NaOH/methanol-based electrolyte, the efficiency of hydrogen formation, a competing reaction of CO₂ reduction, was suppressed to below 4%. The electrochemical CO₂ reduction to methane may be able to proceed efficiently in a hydrophilic environment near the electrode surface provided by sodium cation.     

Construction of a pyrido[4,3-<Emphasis Type="Italic">d</Emphasis>]pyrimidine system on the basis of <Emphasis Type="Italic">N</Emphasis>-cyanobenzamidine and diethyl acetone-1,3-dicarboxylate

Nickel acetate promoted reaction of diethyl acetone-1,3-dicarboxylate with N-cyanobenzamidine led to ethyl 4-amino-6-ethoxycarbonylmethyl-2-phenylpyrimidine-5-carboxylate, upon treatment of which with RNH₂, the corresponding 6-(carbamoylmethyl)pyrimidines were obtained. Cyclization of the latter upon treatment with MeONa afforded 6-R-4-amino-7-hydroxy-2-phenylpyrido[4,3-d]pyrimidin-5(6H)-ones. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2212–2214, November, 2007.     

Theoretical study on H2 elimination pathways of silylenoid H2SiLiF with CH4, NH3, H2O, HF, SiH4, PH3, H2S, and HCl

Ab initio molecular orbital calculations have been performed to explore the reaction potential energy surfaces of silylenoid H₂SiLiF with XH _n hydrides, where XH _n = CH₄, NH₃, H₂O, HF, SiH₄, PH₃, H₂S, and HCl. We have identified a previously unreported reaction pathway on each reaction surface, H₂SiLiF + H-XH _{n − 1} → H _n XSiLiF + H₂, which involves H₂ elimination following the initial formation of an association complex via a four-membered ring transition state to form the substituted three-membered ring silylenoid H _n XSiLiF and a H₂ molecule. This theoretical calculations suggest that (i) for H₂ eliminations there is a very clear trend toward lower activation barriers and more exothermic interactions on going from left to right along a given row in periodic table, and (ii) for the second-row hydrides, the H₂ elimination reactions are less exothermic than for the first-row hydrides and the reaction barriers are lower for X–S and Cl. Compared to the insertions of H₂SiLiF into XH _n , the H₂ elimination pathways should be unfavorable with higher barrier and lower exothermic.     

Oxidation of some catecholamines by sodium N-chloro-p-toluenesulfonamide in acid medium: A kinetic and mechanistic approach

The kinetics of the oxidation of five catecholamines viz., dopamine (A), L-dopa (B), methyldopa (C), epinephrine (D) and norepinephrine (E) by sodium N-chloro-p-toluenesulfonamide or chloramine-T (CAT) in presence of HClO₄ was studied at 30±0.1 °C. The five reactions followed identical kinetics with a first-order dependence on [CAT] _o , fractional-order in [substrate] _o , and inverse fractional-order in [H⁺]. Under comparable experimental conditions, the rate of oxidation of catecholamines increases in the order D>E>A>B>C. The variation of ionic strength of the medium and the addition of p-toluenesulfonamide or halide ions had no significant effect on the reaction rate. The rate increased with decreasing dielectric constant of the medium. The solvent isotope effect was studied using D₂O. A Michaelis-Menten type mechanism has been suggested to explain the results. Equilibrium and decomposition constants for CAT-catecholamine complexes have been evaluated. CH₃C₆H₄SO₂NHCl of the oxidant has been postulated as the reactive oxidizing species and oxidation products were identified. An isokinetic relationship is observed with β=361 K, indicating that enthalpy factors control the reaction rate. The mechanism proposed and the derived rate law are consistent with the observed kinetics.     

RuO<Subscript>4</Subscript>-mediated oxidation of<Emphasis Type="Italic">N</Emphasis>-benzylated tertiary amines. Are amine<Emphasis Type="Italic">N</Emphasis>-oxides and iminium cations reaction intermediates?

N-Benzylmorpholine,-piperidine, and-pyrrolidine (1A-C, resp.) are oxidised by RuO₄ (generated in situ) at both endocyclic and exocyclic (benzylic) N—α-methylene positions to afford lactams (and dioxo-derivatives) and benzaldehyde (and benzoyl derivatives), respectively. The N-oxides of 1A-C, formed by a minor side reaction, are not involved as intermediates. Control experiments showed the transient formation of endo- and exocyclic iminium cations trapped with NaCN as the corresponding nitriles. The proposed course of the RuO₄-mediated oxidation of 1A-C involves the consecutive steps 1⇒iminium cations+cyclic enamine⇒oxidation products. The endocyclic/exocyclic regioselectivity of the oxidation reaction lies between 0.8 (for 1A) and 2.1 (for 1B). The amine cation radical and the N-α-C· carbon-centered radical seem not to be involved.     

Reactions of 9-chloro-1,10-anthraquinone 1-dichlorophosphorylimine with N- and C-nucleophiles

9-Chloro-1,10-anthraquinone 1-dichlorophosphorylimine formed in the reaction of 1-amino-9,10-anthraquinone with PCl₅ followed by dehydrochlorination reacts with primary amines with substitution of chlorine atoms. In the case of aliphatic amines, the reaction occurs further concurrently in two directions: the addition of the amine molecule with the formation of 9,9-di(alkylamino) derivatives of the anthrone and the substitution of hydrogen atom at position 4 with the formation of 4,9-di(alkylamino) derivatives of 1,10-anthraquinone 1-imine. In the case of aromatic amines, 1-amino-9,10-anthraquinone 9-arylimines are the end products. Reactions with the anions of CH-acids containing an alkoxycarbonyl or cyano group occur with substitution in position 9 followed by intramolecular cyclization with the formation of 2-alkoxy- or 2-amino-7H-dibenzo[f,ij]isoquinolin-7-one derivatives, respectively. For preliminary communication, see Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1179–1184, June, 1998.     

Structures and stabilities of HPO<Subscript>2</Subscript> isomers

The potential energy surface of HPO₂ system including eight isomers and twelve transition states is predicated at MP2/6-311++G(d, p) and QCISD(t)/6-311++G(3df,2p)(single-point) levels of theory. On the potential energy surface, cis-HOPO(E1) is found to be thermodynamically and kinetically most stable isomer followed by trans-HOPO(E2) and HPO(O)(C_2v, E3) at 10.99 and 48.36 kJ/mol higher, respectively. Based on the potential energy surface, only E1 and E3 are thermodynamically stable isomers, and should be experimentally observable. The products cis-HPOO(E5) and trans-HPOO(E6) in the first-step reaction of HP with O₂ can isomerize into isomer E1 that has higher stability. The reaction of OH with PO will directly lead to the formation of isomer E1. The computed results are well consistent with the previous experimental studies.     

Condensed isoquinolines 24. Reaction of 6,11-dihydro-13H-isoquino[3,2-<Emphasis Type="Italic">b</Emphasis>]quinazolin-13-one with carbonyl compounds

The reaction of 6,11-dihydro-13H-isoquino[3,2-b]quinazolin-13-one with carbonyl compounds occurs at the C₍₆₎ and/or N₍₅₎ atoms depending on the nature of the reagent and the conditions. Condensation with aldehydes gives 6-arylidene-6,11-dihydro-13H-isoquino[3,2-b]quinazolin-13-ones. Acylation using acid anhydrides or acid chlorides gave 5-acyl-, 6-acyl-, and 5,6-diacyl-5,11-dihydro-13H-isoquino[3,2-b]quinazolin-13-ones depending again on the reaction conditions. Acylation using chloroacetyl chloride is accompanied by an intramolecular alkylation to give 7H,8H-2a, 7a-diaza-cyclopenta[f,g]naphthacene-1,7(2H)-dione. Phenyl isocyanate gave the derivative containing a CONHPh group at position 6. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1509–1520, October, 2007.     

Chemoselectivity of 6-bromo-2-methyl-3,1-benzoxazin-4-one towards amines,Schiff bases,and azines

Summary 6-Bromo-2-methyl-3,1-benzoxazin-4-one (1) undergoes an unusual cleavage at position 4 when it is allowed to react witho-phenylenediamine or anthranilic acid in dry benzene to give the corresponding compounds2–5, respectively. The reaction of1 withSchiffbases and azines results in the formation of the compounds6a–d and8a,b, respectively. The reaction involves a cleavage of theSchiff base or the azine into its amine and arylidene moieties which are smoothly incorporated into1 via nucleophilic attack of the amine at position 4 and condensation of the aldehyde with a reactive methyl group, at position 2 respectively. No displacement of the arylidene segment was observed.

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Zur Chemoselektivität von 6-Brom-2-methyl-3,1-benzoxazin-4-on gegenüber Aminen,Schiffschen Basen und Azinen

Zusammenfassung 6-Brom-2-methyl-3,1-benzoxazin-4-on reagiert mito-Phenylendiamin oder Anthranilsäure in trockenem Benzol unter einer ungewöhnlichen Bindungstrennung zu den Verbindungen2–5. Die Reaktion von1 mitSchiffschen Basen und Azinen führt zu den Verbindungen6a–d und8a,b. Die Reaktion verläuft über eine Spaltung derSchiffschen Base oder des Azins in ihre Amin- und Arylidenreste, die über einen nucleophilen Angriff des Amins an Position 4 und Kondensation des Aldehyds mit der reaktiven Methylgruppe in Position 2 glatt in1 übergeführt werden. Es wurde kein Arylidenaustausch beobachtet.

     

ESR investigation of paramagnetic derivatives of [6-<Emphasis Type="Italic">tert</Emphasis>-butyl-4-(5-<Emphasis Type="Italic">tert</Emphasis>-butyl-2-methyl-3,4-dioxocyclohexa-1,5-dien-1-yl)-3-methylcatecholato]triphenylantimony(V)

A number of paramagnetic derivatives of [6-tert-butyl-4-(5-tert-butyl-2-methyl-3,4-dioxocyclohexa-1,5-dien-1-yl)-3-methylcatecholato]triphenylantimony(v) were investigated by ESR spectroscopy. The reactions of this complex with Cp₂Co or LiCl in the presence of Hg_metal. lead to the formation of free (nonchelated) radical anion semiquiones. Chelated complexes are formed in the case of Tl(Hg), Mn₂(CO)₁₀, Re₂(CO)₁₀, Sn₂Ph₆, Cu(met.), and CuCl + dppfc (dppfc is bis-diphenylphosphinoferrocene). Dedicated to Academician A. L. Buchachenko on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2004–2009, September, 2005.     

Condensed Isoquinolines. 16. Enamine Properties of Benzo[4,5]imidazo[1,2-b]isoquinolin-11(5H)-one in Terms of Its Acylation Reactions

A study has shown that the acylation of benzo[4,5]imidazol[1,2-b]isoquinolin-11(5H)-one occurs at N₍₅₎ or at C₍₆₎ depending on the nature of the acylating reagent and the reaction conditions. It was found that principally C-acylation takes place in the absence of base. The reaction with -halo-substituted carboxylic acid chlorides leads to the formation of C-acylated products which are converted to derivatives of the novel heterocyclic system 7H-2a,6b-diazabenzo[b]cyclopenta[l,m]fluorene-1,7(2H)-dione in the presence of base.     

Sol–gel processing of IrO<Subscript>2</Subscript>–TiO<Subscript>2</Subscript> mixed metal oxides based on a hexachloroiridate precursor

Mixed IrO₂–TiO₂ oxides were prepared by the sol–gel method upon acid-catalysed hydrolysis of an iridium solution in ethanol mixed with titanium tetraethoxide in ethanol. The iridium solution was obtained by reaction of the sodium hexachloroiridate(IV) precursor in the presence of sodium ethoxide in ethanol. Gels were formed in all but the high-Ir samples. Analysis of the dried gels showed minority-phase enrichment at the surface and the presence of Ir(III), while microscopy showed evidence for dispersed iridium-containing nanoparticles (1–20 nm in diameter). XRD powder patterns of the calcined material showed peaks due to a small amount of crystalline NaCl impurity which could be removed by washing. This left amorphous phases, except in the Ir:Ti 3:2 case, which showed evidence for the presence of separate crystalline oxide phases: anatase, IrO₂ and Ti _x Ir_1−x O₂.