- One-pot synthesis of 2-hydroxymethyl-5-methylpyrazine from renewable 1,3-dihydroxyacetone
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An efficient and green method for the synthesis of 2-hydroxymethyl-5-methylpyrazine was achieved from biomass derived 1,3-dihydroxyacetone and diammonium phosphate via a one-pot reaction. The product yield was as high as 72% under optimized conditions of pH = 8.0-9.1 at 90 °C for 1 hour in a dioxane and water mixture as a solvent. A possible reaction mechanism was proposed according to the reaction kinetics, NMR and in situ ATR-IR characterization studies.
- Song, Lei,Zheng, Mingyuan,Pang, Jifeng,Sebastian, Joby,Wang, Wentao,Qu, Minjie,Zhao, Jian,Wang, Xinhong,Zhang, Tao
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Read Online
- Aminoacetone oxidase from Streptococcus oligofermentans belongs to a new three-domain family of bacterial flavoproteins
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The aaoSogene from Streptococcus oligofermentans encodes a 43 kDa flavoprotein, aminoacetone oxidase (SoAAO), which was reported to possess a low catalytic activity against several different L-amino acids; accordingly, it was classified as an L
- Molla, Gianluca,Nardini, Marco,Motta, Paolo,D'Arrigo, Paola,Panzeri, Walter,Pollegioni, Loredano
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- SYNTHESIS AND CATALYTIC OXIDATION OF 2,5-DIMETHYLPYRAZINE
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The classical method for obtaining 2,5-dimethylpyrazine by cyclization of aminoacetone has been improved by use of ammonium persulfate in place of mercuric chloride in the stage of catalytic oxidation of 2,5-dimethyldihydropyrazine.Catalytic vapor phase oxidation of 2,5-dimethylpyrazine gave 5-methylpyrazine-2-aldehyde and pyrazine-2,5-dialdehyde.
- Kastron, V.V.,Iovel', I.G.,Skrastyn'sh, I.P.,Gol'dberg, Yu.Sh.,Shimanskaya, M.V.,Dubur, G.Ya.
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Read Online
- Comparison of pyrazines formation in methionine/glucose and corresponding Amadori rearrangement product model
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The generation of pyrazines in a binary methionine/glucose (Met/Glc) mixture and corresponding methionine/glucose-derived Amadori rearrangement product (MG-ARP) was studied. Quantitative analyses of pyrazines and methional revealed that MG-ARP generated more methional compared to Met/Glc, whereas lower content and fewer species of pyrazines were observed in the MG-ARP model. Comparing the availability of α-dicarbonyl compounds generated from the Met/Glc model, methylglyoxal (MGO) was a considerably effective α-dicarbonyl compound for the formation of pyrazines during MG-ARP degradation, but glyoxal (GO) produced from MG-ARP did not effectively participate in the corresponding formation of pyrazines due to the asynchrony on the formation of GO and recovered Met. Diacetyl (DA) content was not high enough to form corresponding pyrazines in the MG-ARP model. The insufficient interaction of precursors and rapid drops in pH limited the formation of pyrazines during MG-ARP degradation. Increasing reaction temperature could reduce the negative inhibitory effect by promoting the content of precursors.
- Cui, Heping,Deng, Shibin,Hayat, Khizar,Ho, Chi-Tang,Zhai, Yun,Zhang, Qiang,Zhang, Xiaoming
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- Characteristic flavor formation of thermally processed N-(1-deoxy-α-D-ribulos-1-yl)-glycine: Decisive role of additional amino acids and promotional effect of glyoxal
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The role of amino acids and α-dicarbonyls in the flavor formation of Amadori rearrangement product (ARP) during thermal processing was investigated. Comparisons of the volatile compounds and their concentrations when N-(1-deoxy-α-D-ribulos-1-yl)-glycine r
- Zhan, Huan,Cui, Heping,Yu, Junhe,Hayat, Khizar,Wu, Xian,Zhang, Xiaoming,Ho, Chi-Tang
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- Ir-Catalyzed Reversible Acceptorless Dehydrogenation/Hydrogenation of N-Substituted and Unsubstituted Heterocycles Enabled by a Polymer-Cross-Linking Bisphosphine
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The polystyrene-cross-linking bisphosphine ligand PS-DPPBz was effective for the Ir-catalyzed reversible acceptorless dehydrogenation/hydrogenation of N-heterocycles. Notably, this protocol is applicable to the dehydrogenation of N-substituted indoline derivatives with various N-substituents with different electronic and steric natures. A reaction pathway involving oxidative addition of an N-adjacent C(sp3)-H bond to a bisphosphine-coordinated Ir(I) center is proposed for the dehydrogenation of N-substituted substrates.
- Zhang, Deliang,Iwai, Tomohiro,Sawamura, Masaya
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supporting information
p. 5240 - 5245
(2020/07/03)
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- Acceptorless Dehydrogenative Coupling Using Ammonia: Direct Synthesis of N-Heteroaromatics from Diols Catalyzed by Ruthenium
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The synthesis of N-heteroaromatic compounds via an acceptorless dehydrogenative coupling process involving direct use of ammonia as the nitrogen source was explored. We report the synthesis of pyrazine derivatives from 1,2-diols and the synthesis of N-substituted pyrroles by a multicomponent dehydrogenative coupling of 1,4-diols and primary alcohols with ammonia. The acridine-based Ru-pincer complex 1 is an effective catalyst for these transformations, in which the acridine backbone is converted to an anionic dearomatized PNP-pincer ligand framework.
- Daw, Prosenjit,Ben-David, Yehoshoa,Milstein, David
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supporting information
p. 11931 - 11934
(2018/09/27)
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- Synthesis of Pyrazines and Quinoxalines via Acceptorless Dehydrogenative Coupling Routes Catalyzed by Manganese Pincer Complexes
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Base-metal catalyzed dehydrogenative self-coupling of 2-amino alcohols to selectively form functionalized 2,5-substituted pyrazine derivatives is presented. Also, 2-substituted quinoxaline derivatives are synthesized by dehydrogenative coupling of 1,2-diaminobenzene and 1,2-diols. In both cases, water and hydrogen gas are formed as the sole byproducts. The reactions are catalyzed by acridine-based pincer complexes of earth-abundant manganese.
- Daw, Prosenjit,Kumar, Amit,Espinosa-Jalapa, Noel Angel,Diskin-Posner, Yael,Ben-David, Yehoshoa,Milstein, David
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p. 7734 - 7741
(2018/08/03)
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- Reversible Interconversion between 2,5-Dimethylpyrazine and 2,5-Dimethylpiperazine by Iridium-Catalyzed Hydrogenation/Dehydrogenation for Efficient Hydrogen Storage
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A new hydrogen storage system based on the hydrogenation and dehydrogenation of nitrogen heterocyclic compounds, employing a single iridium catalyst, has been developed. Efficient hydrogen storage using relatively small amounts of solvent compared with previous systems was achieved by this new system. Reversible transformations between 2,5-dimethylpyrazine and 2,5-dimethylpiperazine, accompanied by the uptake and release of three equivalents of hydrogen, could be repeated almost quantitatively at least four times without any loss of efficiency. Furthermore, hydrogen storage under solvent-free conditions was also accomplished.
- Fujita, Ken-Ichi,Wada, Tomokatsu,Shiraishi, Takumi
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supporting information
p. 10886 - 10889
(2017/08/30)
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- Vapor phase phototransposition chemistry of dimethylpyrazines and dimethylpyrimidines
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Based on their phototransposition chemistry, the three dimethylpyrazines and four dimethylpyrimidines can be arranged into two groups. 2,5-Dimethylpyrazine, 2,5-dimethylpyrimidine, and 4,6-dimethylpyrimidine constitute a photochemical triad. Irradiation of any one member of the triad in the vapor phase results in the formation of the other two members. The other four isomers, 2,6-dimethylpyrazine, 2,3-dimethylpyrazine, 2,4- dimethylpyrimidine, and 4,5-dimethylpyrimidine constitute a photochemical tetrad. Irradiation of any one member results in the formation of the other three. In addition, 2,4-dimethylpyrimidine and 2,6-dimethylpyrazine also photoisomerize to 3,6-dimethylpyridazine. Irradiation of the last in the vapor state resulted in the four members of the tetrad.
- Pavlik, James W.,Vongakorn, Tharinee,Kebede, Naod
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p. 216 - 228
(2017/11/17)
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- The invention relates to a propylene glycol and liquid ammonia as raw materials for preparing propylene diamine method and apparatus thereof
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The invention relates to a method for preparing propane diamine by taking propylene glycol and liquid ammonia as raw materials. Propylene glycol and liquid ammonia are mixed in a certain ratio and are pumped into a reactor by virtue of a pump, and reaction is carried out in presence of a catalyst and hydrogen. The method for preparing the propane diamine by taking the propylene glycol and liquid ammonia as the raw materials has the advantages that a novel catalyst is adopted, catalytic performance is excellent, and long-time operation can be easily carried out; propylene glycol is subjected to hydroamination for producing a propane diamine product at lower reaction pressure, and reaction conditions are adjusted and changed, so that composition of the product can be flexibly adjusted and changed, selectivity of a target product is improved, a reaction process is simple, one-time investment of a production unit and production cost are reduced, a reaction product and a catalyst can be simply separated, and large-scale continuous industrial production can be easily realized.
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Paragraph 0052-0053; 0089
(2017/08/31)
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- Synthesis and pyrolysis of two flavor precursors of oct-1-en-3-yl methylpyrazinecarboxylates
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To rich flavor additive species of pyrazines, two new compounds of 3,6-dimethyl-2,5-pyrazinedicarboxylic acid 1-octen-3-yl ester (DMPOE) and 3,5,6-trimethyl-2-pyrazinecarboxylic acid 1-octen-3-yl ester (TMPOE) were synthesized by KMnO4 oxidatio
- Lai, Miao,Ji, Xiaoming,Tao, Tao,Shan, Yuanyuan,Liu, Pengfei,Zhao, Mingqin
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p. 1627 - 1638
(2017/05/19)
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- The effects of thermal treatment of ZnO–ZnCr2O4 catalyst on the particle size and product selectivity in dehydrocyclization of crude glycerol and ethylenediamine
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The ZnO–ZnCr2O4 (Zn–Cr–O) sample obtained by decomposition of Zn-Cr hydrotalcite precursor was subjected to the thermal treatment at different temperatures and the physico-chemical properties of the Zn–Cr–O system were compared with
- Sarkari, Reema,Krishna, Vankudoth,Sudhakar, Medak,Rao, Tumula Venkateshwar,Padmasri, Aytam Hari,Srinivas, Darbha,Venugopal, Akula
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p. 602 - 609
(2016/10/18)
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- 1H-pyrrole-2,4-dicarbonyl-derivatives and their use as flavoring agents
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The present invention primarily relates to 1H-pyrrole-2,4-dicarbonyl-derivatives of Formula (I) wherein R1, R2, R3, Z. Z' and J are as defined in the description, to mixtures thereof and to the use thereof as flavoring agents. The compounds in accordance with the present invention are suitable for producing, imparting, or intensifying an umami flavor. The invention further relates to flavoring mixtures, compositions for oral consumption as well as ready-to-eat, ready-to-use and semifinished products, comprising an effective amount of the compound of Formula (I) or of a mixture of compounds of Formula (I) and to specific methods for producing, imparting, modifying and/or intensifying specific flavor impressions.
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- Imidazo[1,2-a]pyridine-ylmethyl-derivatives and their use as flavoring agents
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The present invention primarily relates to imidazo[1,2-a]pyridine-ylmethyl-derivatives of Formula (I) wherein R1, R2, X, W e J are as defined in the description, to mixtures thereof and to the use thereof as flavoring agents. The compounds in accordance with the present invention are suitable for producing, imparting, or intensifying an umami flavor. The invention further relates to flavoring mixtures, compositions for oral consumption as well as ready-to-eat, ready-to-use and semifinished products, comprising an effective amount of the compound of Formula (I) and to specific methods for producing, imparting, modifying and/or intensifying specific flavor impressions.
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- Synthesis of pyrazinyl compounds from glycerol and 1,2-propanediamine over Cu-TiO2 catalysts supported on γ-Al2O3
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Cu-TiO2 catalysts supported on γ-Al2O 3 are prepared and used in glycerol cyclization with 1,2-propanediamine to produce pyrazinyl compounds including 6-hydroxymethyl-2- methylpyrazine, 5-hydroxymethyl-2-methylpyrazine, 2,6-dimethylpyrazine and 2,5-dimethylpyrazine in a fixed-bed system. It is found that glycerol cylclization with 1,2-propanediamine gave a high total yield of pyrazinyl compounds (>80%) over Cu-TiO2/γ-Al2O3 catalyst, and cyclization was through the reactions between activated 1,2-propanediamine and the intermediates from glycerol dehydration and oxidation. In addition, the regioselectivity of the pyrazinyl compounds was mainly controlled by the steric hindrance of the substrates during the cyclization process.
- Li, Xue,Xu, Cheng-Hua,Liu, Chuan-Qi,Chen, Yu,Liu, Jian-Ying
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p. 751 - 754
(2013/07/26)
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- Vapor phase synthesis of methylpyrazine using aqueous glycerol and ethylenediamine over ZnCr2O4 catalyst: Elucidation of reaction mechanism
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A novel method has been developed for the synthesis of methylpyrazine (MP) by using aqueous glycerol and ethylenediamine (EDA) over Zn-Cr catalyst derived from hydrotalcite precursors. The X-ray diffraction analysis of the oven-dried Zn-Cr samples synthesized at various pH ranging from 7 to 11 showed hydrotalcite phase whereas the calcined catalysts displayed ZnO and ZnCr2O 4 phases. The cyclisation activity of Zn-Cr catalyst prepared at pH ～ 9 demonstrated 99.4% conversion of EDA and 94% of glycerol with ～ 72% selectivity to MP at a reaction temperature of 400 °C. This process demonstrates direct utilization of bio-glycerol for the synthesis of MP.
- Sarkari, Reema,Anjaneyulu, Chatla,Krishna, Vankudoth,Kishore, Ramineni,Sudhakar, Medak,Venugopal, Akula
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experimental part
p. 1067 - 1070
(2012/01/15)
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- The effect of pH on the formation of aroma compounds produced by heating a model system containing l-ascorbic acid with l-threonine/l-serine
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The identification of aroma compounds, formed from the reactions of l-ascorbic acid with l-threonine/l-serine at five different pH values (5.00, 6.00, 7.00, 8.00, or 9.55) and 143 ± 2 °C for 2 h, was performed using a SPME-GC-MS technique, and further use
- Yu, Ai-Nong,Zhang, Ai-Dong
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experimental part
p. 214 - 219
(2011/12/14)
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- Formation of pyrazines in maillard model systems of lysine-containing dipeptides
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Whereas most studies concerning the Maillard reaction have focused on free amino acids, little information is available on the impact of peptides and proteins on this important reaction in food chemistry. Therefore, the formation of flavor compounds from the model reactions of glucose, methylglyoxal, or glyoxal with eight dipeptides with lysine at the N-terminus was studied in comparison with the corresponding free amino acids by means of stir bar sorptive extraction (SBSE) followed by GC-MS analysis. The reaction mixtures of the dipeptides containing glucose, methylglyoxal, and glyoxal produced 27, 18, and 2 different pyrazines, respectively. Generally, the pyrazines were produced more in the case of dipeptides as compared to free amino acids. For reactions with glucose and methylglyoxal, this difference was mainly caused by the large amounts of 2,5(6)-dimethylpyrazine and trimethylpyrazine produced from the reactions with dipeptides. For reactions with glyoxal, the difference in pyrazine production was rather small and mostly unsubstituted pyrazine was formed. A reaction mechanism for pyrazine formation from dipeptides was proposed and evaluated. This study clearly illustrates the capability of peptides to produce flavor compounds that can differ from those obtained from the corresponding reactions with free amino acids.
- Van Lancker, Fien,Adams,De Kimpe, Norbert
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scheme or table
p. 2470 - 2478
(2010/09/04)
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- Novel pyrazines from the myxobacterium Chondromyces crocatus and marine bacteria
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The volatiles released by two strains of the myxobacterium Chondromyces crocatus and seven strains of marine Alpha-proteobacteria from the North Sea were collected using the CLSA or SPME headspace methods and analysed by GC-MS. In the extracts of C. crocatus 27 pyrazines were identified, belonging to different classes. 2,5-Dialkylpyrazines and related 3-methoxy-2,5- dialkylpyrazines dominated. Several pyrazines like 2-(1-methylethenyl)-5-(1- methylethyl)-pyrazine (7) and 3-methoxy-2,5-dialkylpyrazines with methyl, isopropyl, isobutyl or sec-butyl side-chains were obtained from natural sources for the first time. It was essential for the identification to rely on synthetic reference materials, which were obtained using Fuerstner's iron-catalysed coupling of chloropyrazines with Grignard reagents or condensation of azido ketones as key steps. The synthetic material allowed the identification of two previously unknown attractants of bacterial origin for the pineapple beetle Carpophilus humeralis, namely 3-methoxy-2-(1-methylpropyl)-5-(2-methylpropyl) pyrazine (17) and 3-methoxy-2,5-bis(1-methylpropyl)pyrazine (52). Several 2,5-dialkylpyrazines were identified in the extracts of the marine Alphaproteobacteria. The unique 2,5-dimethyl-3-(methylsulfanyl)pyrazine (67) represents a new type of natural pyrazine. Our results, together with literature reports, show that pyrazines are an important class of bacterial volatiles which might be more widespread than previously thought. Wiley-VCH Verlag GmbH & Co. KGaA, 2005.
- Dickschat, Jeroen S.,Reichenbach, Hans,Wagner-Doebler, Irene,Schulz, Stefan
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p. 4141 - 4153
(2007/10/03)
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- Synthesis of highly functionalized pyrazines by ortho-lithiation reactions. Pyrazine ladder polymers
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Several novel transformations on sensitive pyrazine cores are disclosed while preparing monomers for condensation polymerizations to planar polypyrazines. Two pyrazine monomers for the step growth polymerization are prepared starting from ethyl acetoacetate and proceeding via pyrazine-2,5-dicarboxylic acid as the common intermediate. The dicarboxylic acid serves as the key intermediate for the preparation of both the A and B components for the step-growth polymerization. A bis(Curtius) rearrangement followed by tert-butyl alcohol capture of the diisocyanate effects the high-yielding conversion of carbonyl moieties to the tert-butoxycarbonyl-protected aryldiamine. Since electrophilic halogenation of the pyrazine nucleus was unsuccessful due to the inherent electron deficiency of pyrazines, a directed ortho-metalation is disclosed using tert-butoxycarbonyl-protected amines and neopentyl glycol acetals as the metalation directing groups. Pd/Cu-catalyzed couplings of diiodopyrazines with distannylpyrazines are utilized for the polymerization schemes. This approach permits the ladder linkages of the planar polymers to (i) form in high yields upon ZnCl2 activation once the polymer backbone is intact, (ii) be substituted so that the newly formed polypyrazines are soluble, unlike many other aromatic ladder polymers, and (iii) contain double-bonded ladder units to keep the consecutive aryl moieties planar which maximizes extended π-conjugation through the polymer backbones, thereby increasing the bandwidths and lowering the optical band gaps.
- Zhang, Carol Y.,Tour, James M.
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p. 8783 - 8790
(2007/10/03)
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- Volatile Compounds Generated from Thermal Reaction of Methionine and Methionine Sulfoxide with or without Glucose
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Methionine and methionine sulfoxide were mixed with or without glucose in distilled water, individually.These solutions were heated in closed sample cylinders at 180 deg C for 1 h.The volatile compounds generated were extracted using methylene chloride and analyzed by GC and GC-MS.Pyrazine compounds, especially 2,5-dimethyl-, 2-ethyl-5-methyl-, trimethyl-, and methylpyrazines were the predominant compounds among those generated from thermal interactions of glucose and methionine or methionine sulfoxide.The formation of methional or those compounds derived for methional was found to be more favorable from the thermal degradation of methionine, whereas the formation of dimethyl polysulfides, especially dimethyl disulfide and dimethyl trisulfide, was found to be more favorable from the thermal degradation of methionine sulfoxide.Glucose was found to have a catalytic effect on the formation of volatile compounds from the thermal degradation of methionine or methionine sulfoxide.Keywords: Methionine; methionine sulfoxide; methional; methyl sulfides; volatiles
- Yu, Tung-Hsi,Ho, Chi-Tang
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p. 1641 - 1646
(2007/10/02)
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- Mechanisms of Formation of Alkylpyrazines in the Maillard Reaction
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The formation of alkylpyrazines was investigated in the reaction of glucose and fructose with -alanine and glycine.The reaction systems were heated for 7 min at 180 deg C.GC-MS and GC-MS/MS data were used to determine the rate of incorporati
- Amrani-Hemaimi, Miriam,Cerny, Christoph,Fay, Laurent B.
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p. 2818 - 2822
(2007/10/03)
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- Electrolytic Oxidation of Ketones in Ammoniacal Methanol in the Presence of Catalytic Amounts of KI
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The indirect electrooxidation of ketones in ammoniacal methanol using iodide ion as a mediator afforded 2,2-dialkyl-2,5-dihydro-1H-imidazoles 3 via an oxidative cyclocoupling of ketimine intermediates formed from ketones and ammonia.The treatment of 3 with dilute HCl gave α-amino ketone hydrochlorides 4 and the parent ketones in good yields.A similar electrooxidation of 3 resulted in the formation of the corresponding 2H-imidazoles 6, which were hydrolyzed to α-diketones and the parent ketones.The same products 6 could also conveniently be obtained by chemical oxidation of 3 with aqueous NaOCl.
- Chiba, Toshiro,Sakagami, Hirotoshi,Murata, Miki,Okimoto, Mitsuhiro
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p. 6764 - 6770
(2007/10/03)
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- SYNTHESIS OF NITROGEN CONTAINING HETEROCYCLES OVER COPPER CHROMITE
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The reactions of 1,2-diaminopropane, 1-amino-2-propanol, 1-amino-2-ethanol, and N-(β-aminoethyl)-1,2-diaminoethane in the gas phase over copper chromite have been investigated with the objective of synthesising nitrogen containing heterocycles.At 240-360
- Meksh, P.A.,Anderson, A.A.,Shimanska, M.
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p. 822 - 828
(2007/10/02)
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- Pt/Al2O3 CATALYSTS IN THE SYNTHESIS OF NITROGEN HETEROCYCLES. CATALYTIC SYNTHESIS OF PYRAZINES
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A study was carried out on the use of Pt/Al2O3 catalysts in the synthesis of pyrazines via the dehydrogenation of piperazines, dehydrodeamination of diamines, and dehydrocyclocondensation of N-hydroxyalkyldiamines.In contrast to the current hypothesis of the intermediate formation of piperazine in the latter two reactions, evidence was found that these reactions proceed through initial dehydrogenation and the dehydrogenated intermediate then undergoes cyclization.Polyalkylpyrazines, formed by the alkylation of the pyrazine ring by hydrogenolysis products, are the major side-products in all the reactions studied.Pyrazines may be obtained in high yield and satisfactory selectivity by selecting suitable modifiers, which enhance the dehydrogenation activity of the catalyst and suppress the hydrogenolysis of the C-N bond.
- Gitis, K. M.,Neumoeva, G. E.,Isagulyants, G. V.
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p. 1308 - 1315
(2007/10/02)
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- EFFECT OF TIME AND TEMPERATURE ON THE PREPARATION OF PYRAZINES IN MODEL REACTIONS OF THE SYNTHESIS OF AROMA-FORMING SUBSTANCES
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The qualitative and quantitative compositions of pyrazines that form in model glucose-ammonia and glucose-ammonia-leucine reactions in a glycerol medium were studied.Reaction conditions were found that ensure the synthesis of 23 alkylpyrazines in total concentration ca. 6 g/kg.The obtained mixture of pyrazines is promising for use in the development of food aroma-forming substances.Keywords: pyrazines, Maillard reaction, capillary gas chromatography.
- Misharina, T. A.,Golovnya, R. V.,Yakovleva, V. N.
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p. 1258 - 1263
(2007/10/02)
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- Process for preparing pyrazines from hydroxyamines
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This invention relates to the reaction of hydroxyamines to form pyrazines by a process comprising reacting said hydroxyamine in the presence of a catalyst which may be a transition metal catalyst optionally containing an alkaline earth metal oxide, or alternatively the catalyst may be a rhodium, ruthenium or palladium-containing compound and a phosphine-containing compound.
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- Process for preparing pyrazines from hydroxyamines
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This invention relates to the cyclocondensation of hydroxyamines to form pyrazines by a process comprising reacting said hydroxyamine in the presence of a catalyst comprising a rhodium, ruthenium or palladium-containing compound and a phosphine-containing compound under mild conditions.
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- ETHYLATION OF PYRAZINES USING ALKYLMETALS, SUCH AS TRIETHYLALUMINUM, DIETHYLZINC, AND TRIETHYLBORANE
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Triethylaluminum, diethylzinc and triethylborane were used for the ethylation of pyrazines.Among these reagents, triethylborane gave the best results.
- Ohta, Akihiro,Ohta, Masakatsu,Igarashi, Yoshiaki,Saeki, Kaemi,Yuasa, Kayo,Mori, Tomoko
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p. 2449 - 2454
(2007/10/02)
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- Studies on the Thermolysis of 2-(2-Hydroxy-2-arylethyl)pyrazines. An Example of a Retro-Ene-Type Reaction
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Several substituted 2-(2-hydroxy-2-arylethyl)pyrazines (1-10) have been prepared and their thermolysis in diglyme and DMF studied.Each of these substrates decomposes to give the parent methylpyrazine and the corresponding aryl aldehyde.Kinetic, isotope effect, and solvent effect studies suggest a mechanism involving a nonpolar concerted six-membered-ring transition state.The degree of proton transfer in the transition state is discussed in detail.Methyl substituents on the pyrazine ring were found to strongly affect the reaction rate.This phenomenon is analyzed interms of the steric and electronic effects induced by the methyl substituents.
- Houminer, Yoram
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p. 999 - 1003
(2007/10/02)
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- Reactions of Halogenomethanes in the Vapour Phase. Part 5. The Reactions of Imidazolines, Anils, and 1-Methylimidazole with Chloroform at 550 deg C, and a Comparison with their Liquid-Phase Reactions with Trichloroacetate Ion or Hexachloroacetone and Base
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The vapor-phase reactions of imidazolines and anils with chloroform at 550 deg C are compared with their liquid-phase reactions in the presence of hexachloroacetone and base or upon thermolysis with trichloroacetate ion.In the vapour-phase reactions imidazolines, unlike imidazoles, gave non-chlorinated pyrimidines, and 1-methyl-imidazole gave 2-cyanopyrrole and the four 3-chlorocyanopyridines.
- Busby, Reginald E.,Khan, Mohammad A.,Khan, Mohammad R.,Parrick, John,Shaw, C. J. Granville
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p. 1431 - 1435
(2007/10/02)
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