Solvent‐Free One‐Step Photochemical Hydroxylation of Benzene Derivatives by the Singlet Excited State of 2,3‐Dichloro‐5,6‐dicyano‐p‐benzoquinone Acting as a Super Oxidant

Photoinduced hydroxylation of neat deaerated benzene to phenol occurred under visible‐light irradiation of 2,3‐dichloro‐5,6‐dicyano‐p‐benzoquinone (DDQ), which acts as a super photooxidant in the presence of water. Photocatalytic solvent‐free hydroxylation of benzene derivatives with electron‐withdrawing substituents such as benzonitrile, nitrobenzene, and trifluoromethylbenzene used as neat solvents has been achieved for the first time by using DDQ as a super photooxidant to yield the corresponding phenol derivatives and 2,3‐dichloro‐5,6‐dicyanohydroquinone (DDQH₂) in the presence of water under deaerated conditions. In the presence of dioxygen and tert‐butyl nitrite, the photocatalytic hydroxylation of neat benzene occurred with DDQ as a photocatalyst to produce phenol. The photocatalytic reactions are initiated by oxidation of benzene derivatives with the singlet and triplet excited states of DDQ to form the corresponding radical cations, which associate with benzene derivatives to produce the dimer radical cations, which were detected by the femto‐ and nanosecond laser flash photolysis measurements to clarify the photocatalytic reaction mechanisms. Radical cations of benzene derivatives react with water to yield the OH‐adduct radicals. On the other hand, DDQ ^{. ?} produced by the photoinduced electron transfer from benzene derivatives reacts with the OH‐adduct radicals to yield the corresponding phenol derivatives and DDQH₂. DDQ is recovered by the reaction of DDQH₂ with tert‐butyl nitrite when DDQ acts as a photocatalyst for the hydroxylation of benzene derivatives by dioxygen.     

Oxidation Reaction of Phenol with H2O2 Catalyzed by Metallomicelles Made of Co(II) and Cu(II) Complexes of Imidazole Groups and Micelle as Mimic Peroxidase

The imidazole derivatives (N,N‐bis(2‐ethyl‐5‐methyl‐imidazole‐4‐ylmethyl) amino‐propane (biap)) and its complexes containing cobalt or copper ion were synthesized in this study. The oxidation reaction of phenol with oxidant H₂O₂ catalyzed by the metallomicelle made of the complexes of imidazole groups and micelle (CTAB, Brij35, LSS) as the mimetic peroxidase was studied. The results show that the reaction rate for the catalytic oxidation of phenol increases by a factor of approximately 1×10⁵ in the metallomicelle over that in the simple micelles or the pure buffer solution at pH=6.9 and 25°C. The catalytic effects changed with H₂O₂, temperature, pH, and surfactant kind in the catalytic reactive process are discussed. A kinetic mathematic model of the phenol oxidation catalyzed by the metallomicelle is proposed.     

Curing kinetics of boron‐containing phenol–formaldehyde resin formed from paraformaldehyde

A boron‐containing phenol–formaldehyde resin (BPFR) was synthesized from boric acid, phenol, and paraformaldehyde. The curing reaction of BPFR was studied by Fourier‐transform infrared spectrometry and differential scanning calorimetry. According to the heat evolution behavior during the curing process, several influencing factors on isothermal curing reaction were evaluated. The results show that the isothermal kinetic reaction of BPFR follows autocatalytic kinetics mechanism, and kinetic parameters m, n, k₁, and k₂, were derived, respectively. In the latter reaction stage, the curing reaction becomes controlled mainly by diffusion. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 638–644, 2002     

Esterification‐nitration of Ortho‐hydroxyphenyl Carboxylic Acids and Benzoic Acids with Cerium(IV) Ammonium Nitrate (CAN)

A convenient and useful esterification was realized, and this reaction proceeded without a dehydrating reagent or water removal equipment. A series of ortho‐hydroxyphenyl carboxylic acids and benzoic acids were transformed to their corresponding methyl esters under CAN/CH₃OH reaction conditions. Whereas in an aprotic solvent, acetonitrile, sp³‐C tethered ortho‐hydroxyphenyl carboxylic acids undergo simultaneous o,p‐dinitration and intramolecular esterification reactions in good yields. Also, 2‐((1 E)‐2‐nitrovinyl)‐4‐nitro‐phenol ( 3e ) showed selective cytotoxicities toward MCF‐7, HEP G2, and HEP 3B cell lines with IC₅₀ values of 23.50, 7.33, and 7.59 ug/mL, respectively.     

Dehydrocoupling and Diels–Alder reactions on siloxane polymers

Dehydrocoupling reactions between linear poly(methylhydrosiloxane) {Me₃SiO–[MeSi(H)O]_n–SiMe₃} and alcohols such as cholesterol, anthracene‐9‐carbinol, (12‐crown‐4)‐2‐carbinol, pyrene‐1‐carbinol, 4‐methyl‐5‐thiazoleethanol, and 4‐pyridilpropanol were introduced under catalytically mild conditions. The degrees of conversion of Si? H bonds in polysiloxane were monitored with ¹H NMR spectra. The reaction of the 9‐methoxyanthracene adduct on siloxane polymers and maleimide derivatives (maleimide, N‐ethylmaleimide, and maleic acid anhydride) produced [2+4]‐cycloadducts in very high yields. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4013–4019, 2002     

Chiral and Achiral Bis（2-oxazolinylphenolato）nickel（Ⅱ） Complexes-Synthesis, Crystal Structure, and Catalytic Properties

Introduction Oxidation was a very important reaction both in synthetic pathways and in industrial processes. Metal-catalyzed oxidation provided excellent alternatives in synthetic processes. However, molecular oxygen has been applied only in a limited number of metal-catalyzed oxidations, because it was very difficult to activate molecular oxygen and most of transition metal complexes were sensitive to oxygen. It was noted that metal-catalyzed Baeyer-Villiger oxidation was a convenient method…     

Synthesis of ultra‐low‐molecular‐weight polyethylene wax using a bulky Ti(IV) aryloxide–alkyl aluminum catalytic system

Complexes of titanium(IV) with bulky phenolic ligands such as 2‐tert‐butyl‐4 methylphenol, 2, 4‐di‐tert‐butyl phenol and 3,5‐di‐tert‐butyl phenol were prepared and characterized. These catalyst precursors, formulated as [Ti(OPh*)_n(OPrⁱ)_4?n] (OPh* = substituted phenol), were found to be active in polymerization of ethylene at higher temperatures in combination with ethylaluminum sesquichloride (Et₃Al₂Cl₃) as co‐catalyst. It was observed that the reaction temperature and ethylene pressure had a pronounced effect on polymerization and the molecular weight of polyethylene obtained. In addition, this catalytic system predominantly produced linear, crystalline ultra‐low‐molecular‐weight polyethylenes narrow dispersities. The polyethylene waxes obtained with this catalytic system exhibit unique properties that have potential applications in surface coating and adhesive formulations. Copyright © 2007 John Wiley & Sons, Ltd.     

Thermal Decomposition of New Mononuclear NiII Complexes with ONNO Type Reduced Schiff Bases and Pseudo Halogens

Mononuclear nickel(II) complexes were prepared by reaction of the three ONNO type reduced Schiff bases bis‐N,N′‐(2‐hydroxybenzyl)‐1,3‐propanediamine (L^HH₂), bis‐N,N′‐(2‐hydroxybenzyl)‐2,2′‐dimethyl‐1,3‐propanediamine (LDM^HH₂), and bis‐N,N′‐[1‐(2‐hydroxyphenyl)ethyl]‐1,3‐propanediamine (LAC^HH₂) with Ni^II ions in the presence of pseudo halides (OCN^–, SCN^– and N₃^–). The complexes were characterized with the use of elemental analyses, IR spectroscopy, and thermal analyses. The molecular structure of one of the complexes was obtained by single‐crystal X‐ray diffraction. The obtained complexes are mononuclear, and a pseudo halide molecule is attached. One of the oxygen atoms of the ligand is in phenolate and the other was in phenol form. According to the thermogravimetry results, it was thought that the pseudo halide thermally detaches from the structure as hydropseudo halide. In azide‐containing complexes an endothermic reaction was observed although the azide group usually decomposes with an exothermic reaction.     

Reactions of Aryl Benzoates with Potassium Aryloxides: Solvent Effects on Reaction Pathway and Kinetics

Temperature dependences of the relative reactivity of potassium aryloxides XC₆H₄O^?K⁺ toward 2,4‐dinitrophenyl benzoate in 50 mol% dimethylformamide (DMF)–50 mol% H₂O mixture have been studied using the competitive reactions technique. Correlation analyses of the relative rate constants k_X/k_H and differences in the activation parameters (ΔΔН^≠ and ΔΔS^≠) of the competitive reactions have revealed the existence of two isokinetic series of the reactions of 2,4‐dinitrophenyl benzoate with potassium aryloxides with electron‐donating substituent (EDS) and electron‐withdrawing substituent (EWS), respectively. We have investigated the effect of the substituent X on the activation parameters for each isokinetic series and concluded that the mechanism of the reactions of 2,4‐dinitrophenyl benzoate with potassium aryloxides XC₆H₄O^?K⁺ in 50 mol% DMF–50 mol% H₂O mixture is the same as in DMF. Analysis of the obtained data with using the method of two‐dimensional reaction coordinate diagram leads to the conclusion that the variation of the solvent from DMF to 50 mol% DMF–50 mol% H₂O mixture affects the reaction pathway. The rate constant k_X for the reaction of 3‐nitrophenyl benzoate with potassium 4‐methoxyphenoxide and the relative rate constants k_X/k_H for the reaction of 3‐nitrophenyl benzoate with potassium aryloxides XC₆H₄O^?K⁺ with EDS were measured in 50 mol% DMF–50 mol% H₂O mixtures at 25°C, and it has been shown that the addition of water to DMF does not change the mechanism but slows down these reactions.     

Influence of the Preparation Procedure on the Catalytic Activity of Gold Supported on Diamond Nanoparticles for Phenol Peroxidation

The catalytic activity of diamond‐supported gold nanoparticle (Au/D) samples prepared by the deposition/precipitation method have been correlated as a function of the pH and the reduction treatment. It was found that the most active material is the one prepared at pH 5 followed by subsequent thermal treatment at 300 °C under hydrogen. TEM images show that Au/D prepared under optimal conditions contain very small gold nanoparticles with sizes below 2 nm that are proposed to be responsible for the catalytic activity. Tests of productivity using large phenol (50 g L ^?1) and H₂O₂ excesses (100 g L ^?1) and reuse gives a minimum TON of 458,759 moles of phenol degraded per gold atom. Analysis of the organic compounds extracted from the deactivated solid catalyst indicates that the poisons are mostly hydroxylated dicarboxylic acids arising from the degradative oxidation of the phenyl ring. By determining the efficiency for phenol degradation and the amount of O₂ evolved two different reactions of H₂O₂ decomposition (the Fenton reaction at acidic pH values and spurious O₂ evolution at basic pH values) are proposed for Au/D catalysis. The activation energy of the two processes is very similar (ranging between 30 and 35 kJ mol^?1). By using dimethylsulfoxide as a radical scavenger and N‐tert‐butyl‐α‐phenylnitrone as a spin trap under aerated conditions, the EPR spectrum of the expected PBN? OCH₃ adduct was detected, supporting the generation of HO^., characteristic of Fenton chemistry in the process. Phenol degradation, on the other hand, exhibits the same activation energy as H₂O₂ decomposition at pH 4 (due to the barrierless attack of HO^. to phenol), but increases the activation energy gradually up to about 90 kJ mol^?1 at pH 7 and then undergoes a subsequent reduction as the pH increases reaching another minimum at pH 8.5 (49 kJ mol^?1).     

Enthalpy–Entropy Correlations in Reactions of Aryl Benzoates with Potassium Aryloxides in Dimethylformamide

Temperature dependences of the relative reactivity of potassium aryloxides XC₆H₄O^?K⁺ toward 4‐nitrophenyl ( 1 ), 3‐nitrophenyl ( 2 ), 4‐chlorophenyl ( 3 ), and phenyl ( 4 ) benzoates in dimethylformamide (DMF) were studied using the competitive reactions technique. The rate constants k_X for the reactions of 1 with potassium 4‐cyanophenoxide, 2 with potassium 3‐bromophenoxide, 3 with potassium 3‐bromo‐, 4‐bromo‐, and unsubstituted phenoxides, 4 with potassium 4‐methoxy‐ and 3‐methylphenoxides were measured at 25°C. Correlation analysis of the relative rate constants k_X/k_H(3‐Me) and differences in the activation parameters (??Н^≠ and ??S^≠) of competitive reactions revealed the existence of six isokinetic series. We investigated the substituent effect of X on the activation parameters for each isokinetic series and concluded that the reactions of aryl benzoates PhCO₂C₆H₄Y with potassium aryloxides in DMF proceed via a four‐step mechanism. The large ρ⁰(Y) and ρ_XY values at 25°C obtained for the reactions of 1–3 with potassium aryloxides with an electron‐donating substituent refer to the rate‐determining formation of the spiro‐σ‐complex. The Hammett plots for the reactions of 1 and 2 exhibit a downward curvature, causing the motion of the transition state for the rate‐determining step according to a Hammond effect as the substituent in aryloxide changes from electron‐donating to electron‐withdrawing. Analysis of data in the terms of two‐dimensional reaction coordinate diagrams leads to the conclusion that significant anti‐Hammond effects arise in the cases of ortho‐substituted and unsubstituted substrates. It was shown that the isokinetic and compensation effects observed for the reactions of aryl benzoates with potassium aryloxides in DMF can be interpreted in the terms of the electrostatic bonding between the reaction centers.     

A one‐dimensional silver(I) coordination polymer based on the 2‐[2‐(pyridin‐4‐yl)‐1H‐benzimidazol‐1‐ylmethyl]phenol ligand exhibiting photoluminescence

A one‐dimensional Ag^I coordination complex, catena‐poly[[silver(I)‐μ‐{2‐[2‐(pyridin‐4‐yl)‐1H‐benzimidazol‐1‐ylmethyl]phenol‐κ²N²:N³}] perchlorate monohydrate], {[Ag(C₁₉H₁₅N₃O)]ClO₄·H₂O}_n, was synthesized by the reaction of 2‐[2‐(pyridin‐4‐yl)‐1H‐benzimidazol‐1‐ylmethyl]phenol (L) with silver perchlorate. In the complex, the L ligands are arranged alternately and link Ag^I cations through one benzimidazole N atom and the N atom of the pyridine ring, leading to an extended zigzag chain structure. In addition, the one‐dimensional chains are extended into a three‐dimensional supramolecular architecture via O—H...O hydrogen‐bond interactions and π–π stacking interactions. The complex exhibits photoluminescence in acetonitrile solution, with an emission maximum at 390 nm, and investigation of the thermal stability reveals that the network structure is stable up to 650 K.     

Oxidative and Photochemical Stability of Ionomers for Fuel‐Cell Membranes

To predict hydroxyl‐radical‐initiated degradation of new proton‐conducting polymer membranes based on sulfonated polyetherketones (PEK) and polysulfones (PSU), three nonfluorinated aromatics are chosen as model compounds for EPR experiments, aiming at the identification of products of HO^.‐radical reactions with these monomers. Photolysis of H₂O₂ was chosen as the source of HO^. radicals. To distinguish HO^.‐radical attack from direct photolysis of the monomers, experiments were carried out in the presence and absence of H₂O₂. A detailed investigation of the pH dependence was performed for 4,4′‐sulfonylbis[phenol] ( SBP ), bisphenol A (= 4,4′‐isopropylidenebis[phenol]; BPA ), and [1,1′‐biphenyl]‐4,4′‐diol ( BPD ). At pH ≥ pK_A of HO^. and H₂O₂, reactions between the model compounds and O₂^.? or ¹O₂ are the most probable ways to the phenoxy and ‘semiquinone’ radicals observed in this pH range in our EPR spectra. A large number of new radicals give evidence of multiple hydroxylation of the aromatic rings. Investigations at low pH are particularly relevant for understanding degradation in polymer‐electrolyte fuel cells (PEFCs). However, the chemistry depends strongly on pH, a fact that is highly significant in view of possible pH inhomogeneities in fuel cells at high currents. It is shown that also direct photolysis of the monomers leads to ‘semiquinone’‐type radicals. For SBP and BPA , this involves cleavage of a C? C bond.     

Kinetics and simulations of reaction between safranine‐O and acidic bromate and role of bromide therein

Safranine‐O, a dye of the phenazinium class, was found to exhibit intricate kinetics during its reaction with bromate at low pH conditions. Under conditions of excess concentrations of acid and bromate, safranine‐O (SA⁺) initially depleted very slowly (k = (3.9 ± 0.3) × 10^?4 M^?3 s^?1) but after an induction time, the reaction occurred swiftly. Bromide exhibited a dual role in the reaction mechanism, both as an autocatalyst and as an inhibitor. The added bromide increased the initial rate of depletion of SA⁺, but delayed the transition to rapid reaction. The overall stiochiometric reaction was found to be 6SA⁺ + 4 BrO₃ ^? = 6SP + 3N₂O + 3H₂O + 6H⁺ + 4Br^?, where SP is 3‐amino‐7‐oxo‐2,8‐dimethyl‐5‐phenylphenazine. The fast kinetics of the reaction between aqueous bromine and safranine‐O (k = (2.2 ± 0.1) × 10³ M^?1 s^?1) are also reported in this paper A 17‐step mechanism, consistent with the overall reaction dynamics and supported by simulations, is proposed and the role of various bromo and oxybromo species is also discussed. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 542–549, 2002     

Synthesis,spectroscopic, thermal and biological aspects of drug‐based copper(II) complexes

A series of novel complexes of the type Cu(II)(L_n)₂(H₂O)₂]^•xH₂O [where L_n = L _1–4 , these ligands being described as: L ₁ , 2‐({4‐[6,7‐dihydrothieno[3,2‐c]pyridin‐5(4H)‐ylsulfonyl]phenylimino}methyl)phenol, x = 1; L ₂ , 2‐({4‐[6,7‐dihydrothieno[3,2‐c] pyridin‐5(4H)‐ylsulfonyl]phenylimino}methyl)‐5‐(methoxy)phenol, x = 2; L ₃ , 5‐chloro‐2‐({4‐[6,7‐dihydrothieno[3,2‐c]pyridin‐5(4H)‐ylsulfonyl]phenylimino}methyl)phenol, x = 2; and L ₄ , 5‐bromo‐4‐chloro‐2‐({4‐[6,7‐dihydrothieno[3,2‐c]pyridin‐5(4H)‐ylsulfonyl]phenylimino} methyl)phenol, x = 1] was investigated. They were characterized by elemental analysis, IR, ¹H‐NMR, ¹³C‐NMR and electronic spectra, magnetic measurements and thermal studies. The FAB‐mass spectrum of [Cu(II)( L ₁ )₂(H₂O)₂]^•H₂O was determined. A magnetic moment and reflectance spectral study revealed that an octahedral geometry could be assigned to all the prepared complexes. Ligands (L_n) and their metal complexes were screened for their in vitro antibacterial activity against Bacillus subtillis, Pseudomonas aeruginosa, Escherichia coli and Serratia marcescens bacterial strains. Kinetic parameters such as order of reaction (n), the energy of activation (E_a), the pre‐exponential factor (A), the activation entropy (ΔS^≠), the activation enthalpy (ΔH^≠) and the free energy of activation (ΔG^≠) are reported. Copyright © 2011 John Wiley & Sons, Ltd.     

Preparation of high‐temperature polyurethane by alloying with reactive polyamide

A series of novel poly(urethane amide) films were prepared by the reaction of a polyurethane (PU) prepolymer and a soluble polyamide (PA) containing aliphatic hydroxyl groups in the backbone. The PU prepolymer was prepared by the reaction of polyester polyol and 2,4‐tolylenediisocyanate and then was end‐capped with phenol. Soluble PA was prepared by the reaction of 1‐(m‐aminophenyl)‐2‐(p‐aminophenyl)ethanol and terephthaloyl chloride. The PU prepolymer and PA were blended, and the clear, transparent solutions were cast on glass substrates; this was followed by thermal treatments at various temperatures to produce reactions between the isocyanate group of the PU prepolymer and the hydroxyl group of PA. The opaque poly(urethane amide) films showed various properties, from those of plastics to those of elastomers, depending on the ratio of the PU and PA components. Dynamic mechanical analysis showed two glass‐transition temperatures (T_g's), a lower T_g due to the PU component and a higher T_g due to the PA component, suggesting that the two polymer components were phase‐separated. The rubbery plateau region of the storage modulus for the elastic films was maintained up to about 250 °C, which is considerably higher than for conventional PUs. Tensile measurements of the elastic films of 90/10 PU/PA showed that the elongation was as high as 347%. This indicated that the alloying of PU with PA containing aliphatic hydroxyl groups in the backbone improved the high‐temperature properties of PU and, therefore, enhanced the use temperature of PU. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3497–3503, 2002     

Selectivity of gas‐phase ion/molecule reaction of carbon dioxide with phenide ions

On contrary to the widely accepted conviction that the m/z 93 ion derived from phenol does not react with CO₂, we demonstrate that it makes an adduct with CO₂ to a small but demonstrable extent. For example, the product‐ion mass spectrum recorded for the m/z 98 ion derived from [²H₆]phenol showed a small peak at m/z 142 when CO₂ was used as the collision gas. The formation of an m/z 137 adduct ion from the m/z 93 ion (generated either directly from phenol, or indirectly from salicylic acid by in‐source decarboxylation) was demonstrated also by multiple‐reaction‐monitoring tandem mass spectrometric experiments. According to literature, the m/z 93 ion derived from salicylic acid does not undergo CO₂ addition because it is deemed to exist only in the phenoxide form. This reaction has been previously proposed as a method for differentiating phenoxide ion from its isomeric hydroxyphenide ions. We propose that the m/z 93 ion, albeit small, exists also as the phenide form together with the predominant phenoxide ion. Copyright © 2014 John Wiley & Sons, Ltd.     

N,O‐chelate aluminum and zinc complexes: synthesis and catalysis in the ring‐opening polymerization of ε‐caprolactone

Reaction between 2‐(1H‐pyrrol‐1‐yl)benzenamine and 2‐hydroxybenzaldehyde or 3,5‐di‐tert‐butyl‐2‐hydroxybenzaldehyde afforded 2‐(4,5‐dihydropyrrolo[1,2‐a]quinoxalin‐4‐yl)phenol (HOL¹NH, 1a) or 2,4‐di‐tert‐butyl‐6‐(4,5‐dihydropyrrolo[1,2‐a]quinoxalin‐4‐yl)phenol (HOL²NH, 1b). Both 1a and 1b can be converted to 2‐(H‐pyrrolo[1,2‐a]quinoxalin‐4‐yl)phenol (HOL³N, 2a) and 2,4‐di‐tert‐butyl‐6‐(H‐pyrrolo[1,2‐a]quinoxalin‐4‐yl)phenol (HOL⁴N, 2b), respectively, by heating 1a and 1b in toluene. Treatment of 1b with an equivalent of AlEt₃ afforded [Al(Et₂)(OL²NH)] (3). Reaction of 1b with two equivalents of AlR₃ (R = Me, Et) gave dinuclear aluminum complexes [(AlR₂)₂(OL²N)] (R = Me, 4a; R = Et, 4b). Refluxing the toluene solution of 4a and 4b, respectively, generated [Al(R₂)(OL⁴N)] (R = Me, 5a; R = Et, 5b). Complexes 5a and 5b were also obtained either by refluxing a mixture of 1b and two equivalents of AlR₃ (R = Me, Et) in toluene or by treatment of 2b with an equivalent of AlR₃ (R = Me, Et). Reaction of 2a with an equivalent of AlMe₃ afforded [Al(Me₂)(OL³N)] (5c). Treatment of 1b with an equivalent of ZnEt₂ at room temperature gave [Zn(Et)(OL²NH)] (6), while reaction of 1b with 0.5 equivalent of ZnEt₂ at 40 °C afforded [Zn(OL²NH)₂] (7). Reaction of 1b with two equivalents of ZnEt₂ from room temperature to 60 °C yielded [Zn(Et)(OL⁴N)] (8). Compound 8 was also obtained either by reaction between 6 and an equivalent of ZnEt₂ from room temperature to 60 °C or by treatment of 2b with an equivalent of ZnEt₂ at room temperature. Reaction of 2b with 0.5 equivalent of ZnEt₂ at room temperature gave [Zn(OL⁴N)₂] (9), which was also formed by heating the toluene solution of 6. All novel compounds were characterized by NMR spectroscopy and elemental analyses. The structures of complexes 3, 5c and 6 were additionally characterized by single‐crystal X‐ray diffraction techniques. The catalysis of complexes 3, 4a, 5a–c, 6 and 8 toward the ring‐opening polymerization of ε‐caprolactone was evaluated. Copyright © 2008 John Wiley & Sons, Ltd.     

Synthesis and Reactions of New Dithiolopyrroles

The title compounds were prepared starting from pyrrolinone 4 . Nucleophilic‐displacement and ring‐closure reactions yielded the dithiolopyrrole 5a , which formed salts with electrophiles ( 7, 8 ) as well as with bases. The crystal structure of 5a was determined. Oxidation of the dithioles 5a and 6a led to S(2)‐oxides ( 10a, 11a ) and the corresponding S(2)‐dioxides ( 10b, 11b ) depending on reaction conditions. The thiosulfinate 10a was converted by a ring‐opening/ring‐closure reaction sequence to the bicyclic sulfinamide 12 . The oxidative addition reactions of [Pt(η²‐C₂H₄) (PPh₃)₂] ( 14 ) with the disulfides 5a and 13 led to the dithiolatoplatinum(II) complexes 15 and 16 , respectively. Complex 16 was characterized structurally. The sulfenato‐thiolato complex 17 was synthesized via reaction of 14 with the thiosulfinate 10a . The thiosulfonato Pt^II complex 18 was prepared by an oxidative insertion of Pt⁰ into the C? S bond of the corresponding thiosulfonate 10b . Furthermore, complex 18 was characterized by single‐crystal X‐ray‐diffraction studies.     

Novel quaternary ammonium borates as latent catalysts for epoxy–phenolic resins

Novel tetrabutylammonium tetrakis(substituted benzoyloxy)borate salts ( 1a – 1d ) were synthesized by the reaction of tetrabutylammonium tetraphenylborate and corresponding substituted benzoic acids. Polyaddition reactions of diglycidyl ether of bisphenol A (DGEBA) and 4,4′‐bisphenol F (44BPF) or bisphenol F (BPF‐D) with the ammonium borates were investigated as model reactions of epoxy/phenol–novolac resin systems with respect to the thermal latency and storage stability of the catalyst. The polyaddition of DGEBA/44BPF with the ammonium borates in diglyme at 150 °C for 6 h proceeded up to 84–94% conversions and gave polymers with number‐average molecular weights of 3750–5750, whereas the polyaddition at 80 °C for 6 h gave less than 9% conversions. The catalytic activity of ammonium borates 1a – 1d depended on the substituent of the phenyl group of the borates, and the order of activity was 1b (p‐OMe) > 1a (? H) > 1c (p‐NO₂) > 1d [3,5‐(NO₂)₂]. The ammonium borate catalyst with the substituent that yielded lower acidity of the corresponding substituted benzoic acid tended to reveal higher activity. In comparison with tetrabutylammonium bromide (TBAB) as a conventional ammonium salt, 1a – 1d revealed better thermal latency. The storage stability of DGEBA/BPF‐D with the ammonium borate catalysts in bulk at 40 °C was better than that with TBAB. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2689–2701, 2002