Polymerization of monoisocyanates by the Pruitt–Baggett adduct

n-Butyl isocyanate (nBIC) was polymerized in bulk by the Pruitt–Baggett adduct (PBA) at ?23, 0.0, and 25.0°C. Polymerization was accompanied by trimerization to the cyclicisocyanurates at all temperatures. Spectroscopic evidences supported the nylon-1 structure for both trimer and polymer. The polymer/trimer ratio and the molecular weight of produced polymers were found to increase with decreasing temperature. The Pruitt–Baggett catalyst (PBC), which is the reaction product of (PBA + H₂O) system, also polymerized nBIC, but with a relatively slower rate. In aromatic and etheric solutions, nBIC was only trimerized by PBA. Copolymerization of nBIC with propylene oxide by PBA and PBC failed. Some selected monoisocyanates were also polymerized by PBA. © 1993 John Wiley & Sons, Inc.     

A study of the effect of the nature of the solvent and temperature on the route of the reaction of thiobenzyl esters of PIII acids with molecular oxygen

The effects of the nature of the solvents, the degree of dilution, the duration of the process, and the temperature on the ratio of the products obtained in the reactions ofS-benzyl diphenylthiophosphinite or S,S-dibenzyl phenyldithiophosphonite with molecular oxygen have been studied. Possible reaction schemes are discussed.Translated fromIzyestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1444–1445, August, 1993.     

Initial steps in the reductive condensation of trichloromethylarenes with hydroxylamine and hydrazines in pyridine

Data concerning the initial steps in the reductive condensation of trichloromethylarenes with hydroxylamine or hydrazines in pyridine have been obtained. High yields of the products of the reductive condensation obtained even at equimolar ratios of trichloromethylarene with hydroxylamine or hydrazine as well as the formation of unusual products,i.e., 4-pyridylhydrazones of substituted benzaldehydes, have been interpreted as the result of the participation of pyridine in the reaction as a reductive agent.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1928–1931, November, 1993     

Haloamidation of alkynes and related reactions using zirconacycles and isocyanates

Zirconacyclopentenes reacted with isocyanates to give aza- or oxazirconacycles which were conveniently coverted into the corresponding haloamidation products of alkynes after halogenation. 1,4-Bistrimethylsilyl substituted zirconacyclopentadiene afforded a low yield of iodoamidation product, whereas zirconium-alkyne complexes stabilized with phosphine gave the iodoamidation products in moderate yields. On the other hand, zirconacyclopentanes reacted with isocyanates to give trimerization products of isocyanate, isocyanurates.     

A convenient and economic method for the synthesis of monohydroxy-pentaalkoxy- and hexaalkoxytriphenylene discotics

A one-step process for the preparation of mono-functionalized triphenylene discotics is presented. Oxidative trimerization of ortho-dialkoxybenzenes using FeCl₃ in nitromethane and a catalytic amount of various acids, furnished monohydroxy-pentaalkoxytriphenylene in addition to hexaalkoxytriphenylene. These products can be easily separated by column chromatography over aluminium oxide.     

Effect of Alkylaluminum Activators on Ethylene Trimerization Based on 2,5‐DMP/Cr(III)/TCE Catalyst System

Ethylene trimerization toward 1‐hexene catalytic system with 2,5‐dimethylpyrrole (2,5‐DMP)/Cr(III)/alkylaluminum/tetrachloroethane (TCE) was investigated. The effects of various cocatalysts on catalytic activity and product selectivity were discussed. The results showed that triethylaluminum (TEA), trimethylaluminum (TMA), tri‐n‐hexylaluminum (TNHA) and tri‐isobutylaluminum (TIBA) were all effective cocatalysts for ethylene trimerization toward 1‐hexene. 2,5‐DMP/Cr(III)/TEA/TCE catalytic system afforded the best results for ethylene trimerization, while reducing the level of by‐product formation. Some specific interaction modes of alkylaluminum with active Cr species in the catalytic cycle were proposed to explain the effect of cocatalyst on catalytic activity and 1‐hexene selectivity.     

Kinetics of thermoset cure and polymerization in the glass transition region

A theoretical approach to thermoset cure kinetics based on Arrhenius kinetics and mobility was developed by considering the activation of the reacting group and chain mobility as elementary steps for reaction. This extended kinetic equation was successfully applied to the curing of an epoxy by an amine, the trimerization of a cyanate, and to the polymerization of methyl methacrylate. Full agreement between theory and experimental data was obtained in all cases. The activation energies for chain mobility were exceptionally low (0.3–1 kJ/mol for bisphenol-A-based epoxy and cyanate) which indicates that the structural units must undergo only small-angle rotational oscillations to allow a reaction. A theoretical time–temperature–transformation (TTT) diagram is also presented. © 1993 John Wiley & Sons, Inc.     

Protonation of leucoemeraldine in the solid state and in solution

The protonation of leucoemeraldine in power form and in N-methylpyrrolidinone (NMP) solution by HCIO₄ and HBF₄ has been studied by x-ray photoelectron spectroscopy (XPS), infrared (IR), and ultraviolet (UV)-visible absorption spectroscopy. In powder form, less than 25% of the amine nitrogens can be protonated in the absence of oxygen. The effects of oxygen on the degree of protonation and the distribution of amine and imine units upon deprotonation of the salt are investigated. The degree of protonation in leuccemeraldine can be increased to about 50% with 3 M HCIO₄, similar to that achievable with emeraldine base in powder form. In NMP solution, leucoemeraldine is easily oxidized by dissolved oxygen. Protonation of both leucoemeraldine and emeraldine base in NMP solutions results in metastable species which gradually undergo deprotonation. The resulting products are affected by the O₂ content of the solutions. © 1993 John Wiley & Sons, Inc.     

Peculiarities of the interaction of dinitrobenzenes witht-BuNHMgBr andt-BuNHLi

Reactions ofm- andp-dinitrobenzenes witht-BuNHMgBr andt-BuNHLi were studied. The reactions afford azo- and azoxy-derivatives and products of nucleophilic substitution.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 739–741, April, 1993.     

有机锂化合物催化合成均三嗪

The imine salt was formed initially by the addition of an organolithium compound to the aromatic nitricle. This type of reaction usually leads to cyclic products, such as triazines. We discussed the mechanism of organolithium compounds catalyzed trimerization of nitriles and study the catalystic charateristics. Using this new method, the yield of triazines was improved.     

Influence of Process Parameters on the Reaction Kinetics of the Chromium‐Catalyzed Trimerization of Ethylene

In this paper we report the results of an extensive experimental kinetic study carried out on the novel ethylene trimerization catalyst system, comprising the chromium source [CrCl₃(thf)₃] (thf=tetrahydrofuran), a Ph₂P‐N(iPr)‐P(Ph)‐N(iPr)H (PNPNH) ligand (Ph=phenyl, iPr=isopropyl), and triethylaluminum (AlEt₃) as activator. It could be shown that the initial activity shows a first‐order dependency on the ethylene concentration. Also, a first‐order dependency was found for the catalyst concentration. The initial activity follows a typical Arrhenius behavior with an experimentally determined activation energy of 52.6 kJ mol^?1. At elevated temperatures (ca. 80 °C), a significant deactivation was observed, which can be tentatively traced back to a ligand rearrangement in the presence of AlEt₃. After a fast initial phase, a pronounced ‘kink’ in the ethylene‐uptake curve is observed, followed by a slow, almost linear, further increase of the total ethylene consumption. The catalyst composition, in particular the ligand/chromium and the cocatalyst/chromium molar ratio, has a strong impact on the catalytic performance of the trimerization of ethylene.     

Niederdruck-Oligomerisation von Mono-Olefinen mit löslichen Nickel/Aluminium-Bimetallkatalysatoren Teil III. Reaktionskinetische Untersuchungen über die Dimerisation und Trimerisation des Áthylens

The kinetics of the di- and trimerization of ethylen in organic solvents under the influence of a homogeneous catalyst containing π-tetramethylcyclobutadiene-nickeldichloride and a prereacted mixture of ethylaluminiumdichloride and tri-n-butylphosphine are reported. The primary reaction product is 1-butene, which is isomerized to 2-butene (cis/trans) during the reaction. The C₆-Olefins are formed by the reaction of ethylene with 1-butene and with the 2-butenes. The following primary reaction products are obtained: 3-hexene (cis/trans), 1-hexene, 2-ethyl-1-butene, 3-methyl-1-pentene and 3-methyl-2-pentene (cis/trans). The effect of other phosphines on the reaction was also studied. The relative composition of the reaction product is strongly dependent upon the amount and the LEWIS base strength of the phosphine present. The results are in accordance with a coordinative mechanism on nickel.     

Catalysis in competing isocyanate reactions. II. Competing phenyl isocyanate reactions catalyzed with N,N′,N″-pentamethyldipropylenetriamine

The kinetics of the N,N′,N″-pentamethyl dipropylene triamine (PMPT)-catalyzed reaction of phenyl isocyanate with n-butanol was studied in acetonitrile between 26.5 and 50°C by measuring the NCO disappearance as well as the formation of the various reaction products by means of the standard dibutylamine back-titration method and the high-performance liquid chromatography (HPLC) method. The resulting products from the phenyl isocyanate and n-butanol reaction were found to be N-butyl phenylcarbamate, N-butyl-α,γ-diphenylallophanate, and triphenylisocyanurate. Trimer formed at the expense of carbamate formation even at a high OH/NCO ratio. Allophanate appeared to be an intermediate in the formation of trimer. PMPT was found to be a urethane and trimerization catalyst for the model reaction of phenyl isocyanate with n-butanol in acetonitrile. The PMPT-catalyzed reaction of phenyl isocyanate with n-butanol in the presence of water in acetonitrile at 50°C was also investigated. The resulting reaction products consisted of n-butyl phenylcarbamate, n-butyl-β,γ-diphenylallophanate, triphenylisocyanurate, sym-triphenylbiuret, and N,N′-diphenylurea. The presence of water retarded the disappearance of NCO groups as well as the trimer formation. Aniline (the product of phenyl isocyanate and water) was detected in the reaction of equivalent amounts of phenyl isocyanate and water in acetonitrile.     

Aromatic polyethers,polysulfones, and polyketones as laminating resins

m-Hexaphenyl ether, diphenyl ether, and 1,3-bis(p-phenoxybenzenesulfonyl)benzene were polymerized with isophthaloyl and terephthaloyl chloride in a Friedel-Crafts type polymerization. The polymers were endcapped with p-cyanobenzyl chloride or had units of 5-cyanoisophthaloyl chloride in the backbone. They were crosslinked effectively, possibly by the trimerization of the nitrile groups to triazines. Model reactions were carried out for each type of polymer.     

Evidence for Carbene Intermediates in Isocyanide Homologation by Aluminium(I)

The C−C bond formation between C1 molecules plays an important role in chemistry as manifested by the Fischer–Tropsch (FT) process. Serving as models for the FT process, we report here the reactions between a neutral Al^I complex (^MeNacNac)Al ( 1 , ^MeNacNac=HC[(CMe)(NDipp)]₂, Dipp=2,6-diisopropylphenyl) and various isocyanides. The step-by-step coupling mechanism was studied in detail by low-temperature NMR monitoring, isotopic labeling, as well as quantum chemical calculations. Three different products were isolated in reaction of 1 with the sterically encumbered 2,6-bis(benzhydryl)-4-Me-phenyl isocyanide (BhpNC). These products substantiate carbene intermediates. The reaction between 1 and adamantyl isocyanide (AdNC) generated a trimerization product, and a corresponding carbene intermediate could be trapped in the form of a molybdenum(0) complex. Tri-, tetra-, and even pentamerization products were isolated with the sterically less congested phenyl and p-methoxyphenyl isocyanides (PhNC and PMPNC) with concurrent construction of quinoline or indole heterocycles. Overall, this study provides evidence for carbene intermediates in FT-type chemistry of aluminium(I) and isocyanides.     

Erzeugung von sieben- und sechsring-alkinen durch photolyse und thermolyse von cyclopropenonen

A six-membered and two seven-membered cycloalkynes, namely 1 – 3, are generated by matrix photolyses of the corresponding cyclopropenones 4 – 6 at about 15 K and characterized by spectroscopic means and in two cases by identification of the trimerization products 9 and 10.     

One-step transformation of tricyclopentabenzene (trindane, C(15)H(18)) to bicyclo(10.3.0)pentadec-1(12)ene- 2,6,7,11-tetrone (C(15)H(18)O(4)) and its aldol product, 12-hydroxy-16-oxatetracyclo(10.3.1.0.(1,5)0(7,11))hexadec-7(11)ene-2,6-dione (C(15)H(18)O(4))

[reaction: see text] Ozonolysis of 1 largely results in 2 and 3, having features similar to several classes of natural products. The retention of the C(15) pericycle suggests preference for the cleavage of pi-bonds endo to the cyclopentane ring. This unique property of trindane offers opportunities for synthesis of complex natural products from this hydrocarbon that can be made in quantity by acid-catalyzed trimerization of cyclopentanone.     

On the trimerization of cyanoacetylene: mechanism of formation of tricyanobenzene isomers and laboratory detection of their radio spectra

In support of a deeper understanding of the chemistry of cyanoacetylene--a known constituent of planetary atmospheres and interstellar space--theoretical and experimental studies address the chemical mechanism of dimerization and trimerization, and provide high-resolution rotational spectra of two of the trimeric products, 1,2,3- and 1,2,4-tricyanobenzene. Analysis of the rotational spectra is particularly challenging because of quadrupolar coupling from three (14)N nuclei. The laboratory rotational spectra provide the basis for future searches for these polar aromatic compounds in interstellar space by radio astronomy.     

Some new transformations of cyclopropylacetylene catalyzed by rhodium,palladium, and cobalt complexes

The linearand cyclic dimerization and trimerization of cyclopropylacetylene were carried out by the action of rhodium, palladium, and cobalt catalysts to give 2,4-dicyclopropyl-1-buten-3-yne, 1,3,6-tricyclopropylfulvene, and 1,3,5-and 1,2,4-tricyclopropylbenzenes.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2360–2362, October, 1989.     

The electronic structure of the HCN dimer and trimer

The electronic structure and energy of dimerization and trimerization of HCN are computed with an STO-3G basis and the results found to be in good agreement with the experimental E. Unlike CNDO/2, this small ab initio basis predicts the correct geometry for the dimer of hydrogen cyanide. The charge redistribution effects found in this H-bond involving a C-H proton donor and sp hybridized acceptor are similar to those found in previous H-bonded studies.