- A general benzylic C-H activation and C-C coupling reaction of zirconocenes mediated by C-N bond cleavage in: tert -butylisocyanide-unusual formation of iminoacyl complexes
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Reactions of the zirconocene alkyne complex [rac-(ebthi)Zr(η2-Me3SiC2SiMe3)] (rac-(ebthi) = rac-1,2-ethylene-1,1′-bis(η5-tetrahydroindenyl)) with tert-butylisocyanide and methylbenzenes were investigated. Depending on the stoichiometry, the solvent and the reaction temperature different products were obtained. Starting with the end-on coordination of the isocyanide to the zirconium centre (2), elevated reaction temperatures and an excess of tert-butylisocyanide resulted after the elimination of the alkyne in the formation of zirconocene η2-iminoacyl cyanide complexes 3a-d. These complexes are formed by coupling with a benzyl fragment through C-H bond activation of a methyl group of methylbenzene. The dimeric cyanide bridged zirconocene complex 4 is formed as a side-product of this process. The unexpected dimer and the heterometallacycles were fully characterised, including X-ray crystallography.
- Arndt, Perdita,Rei?, Melanie,Spannenberg, Anke,Schünemann, Claas,Rei?, Fabian,Beweries, Torsten
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Read Online
- A NEW ROUTE TO THE 4H-1,2-OXAZETE RING SYSTEM BY THE STEREOSPECIFIC OXIDATION OF (Z)-3,3-DIMETHYL-1,1-BIS(METHYLTHIO)-2-BUTANONE OXIME
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A new synthesis of a funktionalized 4H-1,2-oxazete by oxidation of α,α-bis-(alkylthio) oxime is described.
- Corkins, H. Glenn,Storace, Lou,Osgood, Edmond R.
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Read Online
- Cyclometalated Platinum(II) Complexes with Nitrile and Isocyanide Ligands: Synthesis, Structure, and Photophysical Properties
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Abstract: A series of cyclometalated platinum(II) complexes with nitrile and isocyanide ligands (RCN and RNC; R = t-Bu, Bn, Ph) have been synthesized in 60–80% yields from the dimer [{Pt(ppy)Cl}2] (Hppy is 2-phenylpyridine) and the corresponding nitriles and isocyanides. The structure of the synthesized complexes was determined by mass spectrometry, IR and NMR spectroscopy, and X-ray diffraction. The contributions of different intermolecular interactions to the crystal packing were estimated by Hirshfeld surface analysis. Photophysical properties of the synthesized complexes in solution and solid state were studied.
- Katkova,Eliseev,Mikherdov,Sokolova,Starova,Kinzhalov
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p. 393 - 400
(2021/04/26)
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- NHC-catalyzed silylative dehydration of primary amides to nitriles at room temperature
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Herein we report an abnormal N-heterocyclic carbene catalyzed dehydration of primary amides in the presence of a silane. This process bypasses the energy demanding 1,2-siloxane elimination step usually required for metal/silane catalyzed reactions. A detailed mechanistic cycle of this process has been proposed based on experimental evidence along with computational study.
- Ahmed, Jasimuddin,Hota, Pradip Kumar,Maji, Subir,Mandal, Swadhin K.,Rajendran, N. M.
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supporting information
p. 575 - 578
(2020/01/29)
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- SO2F2-Mediated one-pot cascade process for transformation of aldehydes (RCHO) to cyanamides (RNHCN)
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A simple, mild and practical cascade process for the direct conversion of aldehydes to cyanamides was developed featuring a wide substrate scope and great functional group tolerability. This method allows for transformations of readily available, inexpensive, and abundant aldehydes to highly valuable cyanamides in a pot, atom, and step-economical manner with a green nitrogen source. This protocol will serve as a robust tool for the installation of the cyanamide moiety in various complicated molecules.
- Ding, Chengrong,Ge, Shuting,Wei, Junjie,Zhang, Guofu,Zhao, Yiyong
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p. 17288 - 17292
(2020/05/18)
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- Chemical Vapor Deposition of Phase-Pure Uranium Dioxide Thin Films from Uranium(IV) Amidate Precursors
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Homoleptic uranium(IV) amidate complexes have been synthesized and applied as single-source molecular precursors for the chemical vapor deposition of UO2 thin films. These precursors decompose by alkene elimination to give highly crystalline ph
- Straub, Mark D.,Leduc, Jennifer,Frank, Michael,Raauf, Aida,Lohrey, Trevor D.,Minasian, Stefan G.,Mathur, Sanjay,Arnold, John
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p. 5749 - 5753
(2019/04/16)
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- Double metal cyanides as heterogeneous Lewis acid catalysts for nitrile synthesis: Via acid-nitrile exchange reactions
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A series of transition metal-based double metal cyanides (DMCs) were studied as catalysts for the synthesis of nitriles via acid-nitrile exchange reaction. The best nitrile yields were obtained with Co3[Co(CN6)]2 DMC, which proved to be a versatile, stable, reusable and highly active catalyst, exhibiting an activity comparable to that of homogeneous Lewis acid catalysts.
- Marquez, Carlos,Corbet, Matthieu,Smolders, Simon,Marion, Philippe,De Vos, Dirk
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supporting information
p. 12984 - 12987
(2019/11/05)
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- OXIDATIVE CONVERSION OF ALIPHATIC ALDEHYDES TO NITRILES USING OXOAMMONIUM SALT
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The present invention relates to an oxidative transformation method of aliphatic benzaldehydes to nitriles using NH_4OAc through oxoammonium salts. By using stoichiometric amounts of oxoammonium salts to establish optimal reaction conditions associated with the oxidative conversion of aliphatic benzaldehydes to nitriles, high yields of nitrile can be selectively obtained, and the oxoammonium salts used can be oxidized and reused in a simple method.COPYRIGHT KIPO 2020
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Paragraph 0055-0063; 0136-0142
(2019/12/10)
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- Oxoammonium salt-mediated oxidative nitriles synthesis from aldehydes with ammonium acetate
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An efficient and scalable route for the synthesis of nitriles was developed by oxoammonium salt (4-acetamido-2,2,6,6-tetramethylpiperidine-1-oxoammonium tetrafluoroborate) mediated oxidative conversion of aldehydes with NH4OAc. A variety of aliphatic aldehydes as well as benzaldehydes were converted into the corresponding nitriles in high yields. The nitroxyl radical which is the reduced species of the used oxoammonium salt was recovered by simple acid-base extraction for the recycling.
- Kim, Myeong Jin,Mun, Junyoung,Kim, Jinho
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supporting information
p. 4695 - 4698
(2017/11/17)
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- Dehydration of Aldoximes Using PhSe(O)OH as the Pre-Catalyst in Air
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PhSe(O)OH was found to be a good pre-catalyst for aldoxime dehydrations in open air. Compared with the previously reported (PhSe)2-H2O2 system, it is more stable and milder, affording broader application scopes due to a higher functional group tolerance. The control experiments for mechanism study disclosed that air was the key factor for the reaction to maintain enough concentration of PhSeOH, which should be the real catalytic species.
- Zhang, Xu,Sun, Jingjing,Ding, Yuanhua,Yu, Lei
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supporting information
p. 5840 - 5842
(2015/12/11)
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- Reactivity and Moessbauer spectroscopic characterization of an Fe(IV) ketimide complex and reinvestigation of an Fe(IV) norbornyl complex
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Thermolysis of Fe(Ni=CtBu2)4 (1) for 8 h at 50 °C generates the mixed valent Fe(III)/Fe(II) bimetallic complex Fe2(Ni=CtBu2)5 (2) in moderate yield. Also formed in this reaction
- Lewis, Richard A.,Smiles, Danil E.,Darmon, Jonathan M.,Stieber, S. Chantal E.,Wu, Guang,Hayton, Trevor W.
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p. 8218 - 8227
(2013/08/23)
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- A one-pot conversion of carboxylic acids into nitriles catalysed by PEG400 under microwave irradiation
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A new efficient method for the synthesis of nitriles is reported. Carboxylic acids were converted into nitriles by a onepot reaction with hydroxylamine sulfate and zinc catalysed by PEG400 under microwave irradiation in excellent yields. The most suitable condition was 20 minutes under the microwave power of 231 W with 5 mol% PEG400.
- Cao, Yu-Qing,Qu, An-Li,Liu, Rui-Yan,Duan, Chun-Ming
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experimental part
p. 414 - 415
(2010/12/19)
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- Thermal rearrangements of (arylimino)diaziridines by simultaneous cascades of pericyclic reactions
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(Arylimino) diaziridines rearrange in several cascade reactions at temperatures 60-100 °C. Those that possess unoccupied ortho positions yield fluorescent: 3-amino-2H-indazoles and 2-amino-1H-benzimidazoles. If both ortho positions are blocked by methyl groups, indazoles are not formed and deeply yellow 2-imino-2,3-dihydro-3aH-benzimidazoles are formed, which partly dimerize through Diels-Alder reaction or regenerate the aromatic system, by formal loss of CH2. In addition, one of the methyl groups of 2,6-dimethylphenyl rings is involved in a [1,7] H shift affording orthoquinonoid intermediates which undergo 1,6-electrocyclization to furnish 2-amino-3,4-dihydroquinazolines. The formation of fivemembered ring heterocycles is interpreted in terms of valence isomerization by [1,3] N shift to yield elusive 1-ary 1-3iminodiaziridines as first step. These immediately experience triaza-Cope rearrangement to benzimidazole derivatives or electrocyclic opening of the N-C bond to generate conjugated azomethine imines (1,5-dipoles), followed by their 1,5electrocyclization to indazoles. First-order rate constants of the decay of (arylimino) diaziridines refer to the [1,3] N shifts as rate-determining steps. They are larger than the corresponding rate constants for alkylsubstituted iminodiaziridines.
- Quast, Helmut,Ross, Karl-Heinz,Philipp, Gottfried
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scheme or table
p. 2212 - 2217
(2010/06/20)
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- Propylphosphonic anhydride (T3P): A remarkably efficient reagent for the one-pot transformation of aromatic, heteroaromatic, and aliphatic aldehydes to nitriles
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Propylphosphonic anhydride has been demonstrated to be an efficient reagent for the transformation of aromatic, heteroaromatic, and aliphatic aldehydes to respective nitriles in excellent yields. This procedure offers simple and one-pot access to nitriles and highlights the synthetic utility of T3P as a versatile reagent in organic chemistry. Georg Thieme Verlag Stuttgart - New York.
- Augustine, John Kallikat,Atta, Rajendra Nath,Ramappa, Balakrishna Kolathur,Boodappa, Chandrakantha
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experimental part
p. 3378 - 3382
(2010/03/03)
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- Syntheses and15N NMR Spectra of Iminodiaziridines - Ring-Expansions of 1-Aryl-3-iminodiaziridines to 1H- and 3aH-Benzimidazoles, 2H-Indazoles, and 5H-Dibenzo[d,f] [1,3]diazepines
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Iminodiaziridines are synthesized, by (i) 1,3-dehydrochlorination with potassium, teri-butoxide of N-chloroguanidines, generated in situ from. N,N′,N″-substituted guanidines with tert-butyl hypochlorite, and (ii) base-mediated 1,3-elimination of sulfuric acid from N,N',N″- substituted hydroxyguanidine O-sulfonic acids. At elevated temperatures, (alkylimino)diaziridines undergo valence isomerization by 1,3shift, [2+1] cycloelimination to afford isocyanides and diazenes, and ring-opening elimination to yield alkylideneguanidines. N′-Aryl-N-hydroxyguanidine O-sulfonic acids furnish (N-arylimino)diaziridines, but no 1-aryl-3- iminodiaziridines, instead giving rearranged isomere. Precursors containing perdeuterated feri-butyl groups give rearranged products that show complete scrambling. This indicates that l-aryl-3iminodiaziridines are intermediates that undergo very rapid I degenerate valence isomerization. Provided that the ortho aryl positions are substituted, high yields of (arylimino)diaziridines are obtained, along with 2-imino-2,3-dihydro-3aHbenzimidazoles, Otherwise, 2-amino-lH-benzimidazoles and strongly fluorescent 3-amino-2H-indazoles, originating from rearrangements of the elusive l-aryl-3-iminodiaziridines, predominate. N',N″-Diaryl-N-hydroxyguanidine O-sulfonic acids give only rearranged products: a 2-amino-1H-benzimidazole and a 6-amino-5H-dibenzo[d,f][1. 3]diazepine if aryl = phenyl, or a 2-imino-2,3-dihydro-3aH-benzimidazole if aryl = mesityl. 3aH-Benzimidazoles slowly dimerize through Diels-Alder reactions. 15N NMR signals were assigned, to the syn and anti ring nitrogen atoms of iminodiaziridines with the help of a combination of homonuclear NOE and HNHMBC or HN-gHMBC experiments.
- Quast, Helmut,Ross, Karl-Heinz,Philipp, Gottfried,Hagedorn, Manfred,Hahn, Harald,Banert, Klaus
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supporting information; experimental part
p. 3940 - 3952
(2010/03/01)
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- Laboratory-scale synthesis of nitriles by catalysed dehydration of amides and oximes under flash vacuum pyrolysis (FVP) conditions
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Dehydration of amides and oximes can be catalysed by 3 A molecular sieves or by tungsten trioxide under flash vacuum pyrolysis (FVP) conditions. This provides a convenient synthesis of aliphatic, aromatic, and heterocyclic nitriles, generally in excellent yields under mild, neutral, and short contact time conditions. Georg Thieme Verlag Stuttgart.
- Campbell, Jacqueline A.,McDougald, Graham,McNab, Hamish,Rees, Lovat V. C.,Tyas, Richard G.
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p. 3179 - 3184
(2008/04/03)
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- A simple one-pot procedure for the direct conversion of alcohols into alkyl nitriles using TsIm
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A convenient and efficient one-pot preparation of nitriles from alcohols using N-(p-toluenesulfonyl)imidazole (TsIm) is described. In this method, treatment of alcohols with a mixture of NaCN, TsIm and triethylamine in the presence of catalytic amounts of tetra-n-butylammonium iodide (TBAI) in refluxing DMF furnishes the corresponding alkyl nitriles in good yields. This methodology is highly efficient for various structurally diverse alcohols with selectivity for ROH: 1° > 2° > 3°.
- Soltani Rad, Mohammad Navid,Khalafi-Nezhad, Ali,Behrouz, Somayeh,Faghihi, Mohammad Ali
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p. 6779 - 6784
(2008/02/13)
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- Reaction of primary amines with Pt/C catalyst in water under microwave irradiation: A convenient synthesis of secondary amines from primary amines
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Upon microwave irradiation in water, Pt/C converts primary amines into secondary amines in good yield via retro-reductive and reductive amination.
- Miyazawa, Akira,Saitou, Kaori,Tanaka, Kan,G?dda, Thomas M.,Tashiro, Masashi,Prakash, G. K. Surya,Olah, George A.
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p. 1437 - 1439
(2007/10/03)
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- Zirconium-mediated conversion of amides to nitriles: A surprising additive effect
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Chloride coordination is the key: Dimethylzirconocene reacts with amides to form methylzirconium amide complexes. On heating, in the presence of a chloride source, these compounds are converted into N-acylimidozirconocene complexes that react intramolecularly to form the corresponding nitrile compounds (see scheme; Cp = C5H5). Mechanistic studies reveal that chloride coordination to zirconium is required for this transformation to occur.
- Ruck, Rebecca T.,Bergman, Robert G.
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p. 5375 - 5377
(2007/10/03)
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- Aldehyde detection by chromogenic/fluorogenic oxime bond fragmentation
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Amination of 4-nitrophenol, umbelliferone and 4-methylumbelliferone gave the corresponding oxyamines 1-3. These oxyamines react with aldehydes and ketones to form oximes. In the case of aliphatic aldehydes and electron-poor aromatic aldehydes, the oximes undergo base-catalyzed fragmentation in aqueous buffer in the presence of bovine serum albumin to give the parent phenols, which is the acyclic analog of Kemp's elimination reaction of 5-nitrobenzisoxazole 28. The process can be used as a spectrophotometric assay for formaldehyde under aqueous neutral conditions.
- Salahuddin, Syed,Renaudet, Olivier,Raymond, Jean-Louis
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p. 1471 - 1475
(2007/10/03)
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- Conversion of Alcohols, Thiols, and Trimethysilyl Ethers to Alkyl Cyanides Using Triphenylphosphine/2,3-Dichlorol-5,6-dicyanobenzoquinone/n-Bu 4NCN
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Triphenylphosphine and 2,3-dichloro-5,6-dicyanobenzoquinone afford an adduct, which in the presence of n-Bu4NCN converts alcohols, thiols, and trimethylsilyl ethers into their corresponding alkyl cyanides in good to excellent yields at room tem
- Iranpoor, Nasser,Firouzabadi, Habib,Akhlaghinia, Batool,Nowrouzi, Najmeh
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p. 2562 - 2564
(2007/10/03)
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- Thermal decomposition of O-benzyl ketoximes; role of reverse radical disproportionation
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Thermolyses of seven dialkyl, two alkyl-aryl and two diaryl O-benzyl ketoxime ethers, R1R2C=NOCH2Ph, have been examined in three hydrogen donor solvents: tetralin, 9,10-dihydrophenanthrene, and 9,10-dihydroanthracene. All the oxime ethers gave the products expected from homolytic scission of both the O-C bond (viz., R1R2C=NOH and PhCH3) and N-O bond (viz., R1R2C=NH and PhCH2OH). The yields of these products depended on which solvent was used and the rates of decomposition of the O-benzyl oxime ethers were greater in 9,10-dihydrophenanthrene and 9,10-dihydroanthracene than in tetralin. These results indicated that a reverse radical disproportionation reaction in which a hydrogen atom was transferred from the solvent to the oxime ether, followed by β-scission of the resultant aminoalkyl radical, must be important in the latter two solvents. Benzaldehyde was found to be an additional product from thermolyses conducted in tetralin. This, and other evidence, indicated that another induced decomposition mode involving abstraction of a benzylic hydrogen atom, followed by β-scission of the resulting benzyl radical, became important for some substrates. Participation by minor amounts of enamine tautomers of the oxime ethers was shown to be negligible by comparison of thermolysis data for the O-benzyloxime of bicyclo[3.3.1]nonan-9-one, which cannot give an enamine tautomer, with that of the O-benzyloxime of cyclohexanone.
- Blake, Jessie A.,Ingold, Keith U.,Lin, Shuqiong,Mulder, Peter,Pratt, Derek A.,Sheeller, Brad,Walton, John C.
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p. 415 - 420
(2007/10/03)
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- Reduction of amides with NaBH4 in diglyme at 162°C
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High temperature (162°C) reductions of aromatic amides were studied to extend the useful range of functional group transformations by NaBH4. Primary aromatic amides were reduced to the amines with NaBH4-diglyme at 162°C. Reduction proceeds via fast initial loss of hydrogen, followed by formation of the corresponding nitrile, which is then more slowly reduced to the amine. N-Methylbenzamide is not reduced under these conditions, but it is reduced to benzylmethylamine when LiCl is added to NaBH4-diglyme at 162°C. LiCl addition raised the rate of primary aromatic amide and aromatic nitrile conversions to both the nitrile, first, and the amine. An intermediate was isolated from the reaction of N-benzylformamide with NaBH4-LiCl in diglyme at 162°C. It was examined by 1H NMR, atomic absorption, IR and thermal decomposition. Possible structures are proposed. A mechanism for the reduction of primary aromatic amides is proposed based on the initial evolution of one mole equivalent of hydrogen and formation of the nitrile prior to further reduction to amine.
- Zhu, Hua-Jie,Lu, Kai-Tao,Sun, Guang-Ri,He, Jin-Bao,Li, Hai-Qing,Pittman Jr., Charles U.
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p. 409 - 413
(2007/10/03)
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- About four new trityl-substituted α-lactams
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This investigation comprises the synthesis, a description of the physical and spectroscopic properties, determination of the limits of thermal stability, and reactions with protic and aprotic nucleophiles of four new trityl-substituted α-lactams. With the exception of 3,3-dimethyl-1-tritylaziridin-2-one (4a), which is unstable at room temperature, all new compounds have been fully characterized.
- Lengyel, Istvan,Cesare, Victor,Adam, Ian,Taldone, Tony
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- Push-pull mechanism of hydrodenitrogenation over silica-supported MoP, WP, and MoS2 hydroprocessing catalysts
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The mechanism of liquid-phase catalytic hydrodenitrogenation at 3.1 MPa on silica-supported molybdenum phosphide, MoP/SiO2, and tungsten phosphide, WP/SiO2, was studied using a series of pentylamines of different structures. The reactivity pattern suggested that removal of nitrogen occurred primarily by an E2 elimination mechanism involving acidic and base sites on the catalyst surfaces in a push-pull process. Infrared spectroscopy and temperature-programmed reaction studies of ethylamine indicated that alkyl ammonium species formed on Bronsted acid sites were intermediates in the reaction. Similar results were obtained with a reference MoS2/SiO2 sample tested at the same conditions. This suggested that sulfur was probably present on the active surface and assisted in the removal of sulfur.
- Clark,Wang,Deck,Oyama
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p. 116 - 126
(2007/10/03)
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- Formation of nitrile ylides in the addition of singlet carbene to nitrile compounds - Laser flash photolysis of (biphenyl-4-yl)-chlorodiazirine in the presence of nitrile compounds
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Formation of a nitrile ylide (NY) by addition of a singlet carbene to a nitrile compound was studied by laser flash photolysis (LFP) of (biphenyl-4-yl)chlorodiazirine (BCD) in the presence of nitrile compounds. Although the generated (biphenyl-4-yl)chlorocarbene (BCC) forms a NY by addition to a nitrile compound in an equilibrium reaction, the absorption spectrum of the NY can be measured only in the LFP of BCD in the presence of 2,4,6-trimethoxybenzonitrile. The equilibrium constants for the NY formation in the addition of BCC to propiononitrile or pivalonitrile were determined to be 0.45 and 0.37 M-1 at 295 K, respectively. The reactivity of NY towards olefins seems to be substantially lower than those of BCC. The reaction of BCC with 2,3-dimethylbut-2-ene was carried out in 2,2,4-trimethylpentane and propionitrile in the temperature range of ca. 170 to 300 K. In both solvents, the rate constants increased with decreasing temperature and the maximum value appeared at around 210 K. Using the difference in the rate constants, the free energy difference for the equilibrium constant was also estimated to be ca. 4.2 kJ mol-1.
- Naito, Ikuo,Oku, Akira,Fijiwara, Yoshihisa,Tanimoto, Yoshifumi
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p. 1051 - 1056
(2007/10/03)
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- An elimination reaction of N-carbomethoxy-N,N-dimethylhydrazonium salts to alkyl nitriles
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A new kind of elimination of hydrazonium salts to alkyl nitriles has been developed. The reaction of hydrazones and chloroformates results in the formation of hydrazonium salts, which react in situ with water to afford alkyl nitriles. The elimination is adapted to a range of solvents and gives good yields of α-secondary and tertiary alkyl-substituted nitriles.
- Xiao, Zejun,Timberlake, Jack W.
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p. 12715 - 12720
(2007/10/03)
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- Limitations on the Persistence of Iminoxyls: Isolation of tert-Butyl 1,1-Diethylpropyl Ketiminoxyl and Related Radicals
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A series of iminoxyl radicals of the general formula R(C=NO?)R1, with R and R1 usually tertiary, was synthesized in a search for radicals of increased persistence. Three new radicals were isolated as blue liquids: Et3C(C=NO?)Bu-t (1), t-C5H11(C=NO?)Bu-t (2), and (t-C5H11)2C=NO? (3). Oxidation of oximes Et3C(C=NOH)Ph (4H), PhCH2CMe2(C=NOH)Bu-t (5H), PhCMe2(C=NOH)Bu-t (6H), and Me2CH(C=NOH)C5H11-t (7H), among others, did not lead to isolable iminoxyls. A new, convenient synthesis of symmetrical tertiary imines from tert-RCl, tert-RCN, and Na is described. Radical t-Bu2C=NO? (8) and cyclohexene readily gave the allylic substitution product, 2,2,4,4-tetramethyl- 3-hexanone O-(2′-cyclohexen-1′-yl)oxime.
- Eisenhauer, Brian M.,Wang, Minghui,Labaziewicz, Henryk,Ngo, Maria,Mendenhall, G. David
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p. 2050 - 2053
(2007/10/03)
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- The facile fragmentation of trifluoroacetyl groups to nitriles
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Trifluoroacetyl groups attached to a carbon atom devoid of hydrogen undergo facile, high-yield conversion to nitriles by reaction with MeAlClNH2, followed by KOtBu, in a 'one-pot' reaction sequence.
- Kende, Andrew S.
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p. 4035 - 4038
(2007/10/02)
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- Small Rings, 89. - An Alternative Synthesis of Tetra-tert-butyltetrahedrane
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Cyclopropenyldiazomethane 3 is an ideal precursor for tetra-tert-butyltetrahedrane (6).Both, photochemical and thermal decomposition of 3 lead to cyclobutadiene 7, which can be photoisomerized to tetrahedrane 6.Tetra-tert-butyltetrahedrane (6) is also formed directly by a cheletropic cycloaddition of the carbenic center to the cyclopropene double bond in carbene 4.This is the first example for the synthesis of a tetrahedrane, which does not occur via the corresponding cyclobutadiene.The formation of pyridazine 10 dominates the thermolysis of 3.Azete 12 is obtained both by photolysis as well as by thermolysis of Dewar-pyridazine 11, the irradiation product of 10. - Key Words: Cyclobutadiene / Tetrahedrane / Azete / Cyclopropenyldiazomethane / Valence isomers of pyridazine
- Maier, Guenther,Fleischer, Frank
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p. 169 - 172
(2007/10/02)
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- Method for converting amides to nitriles and nitriles to amides
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A process which comprises contacting and catalytically reacting under essentially anhydrous conditions in the liquid phase an amide with a nitrile according to the equation: where R and R1 are not the same and are each selected from (1) H, hydrocarbyl, a hydrocarbyl group substituted with: one or more of F, Cl, Br, I, amido, cyano, formyl, hydrocarbylcarbonyl, hydrocarbyloxy, hydrocarbyloxycarbonyl, hydrocarbylcarbonyloxy and dihydrocarbylamino, and (2) any of group (1) where one or more H atoms are substituted by a deuterium atom,
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- Thermal Reorganization and Cycloaddition Reactions of a Chiral, Non-Racemic Aziridinone (α-Lactam) and Ab Initio Calculations of the C2H3NO Energy Hypersurface
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The thermal reorganization of the racemic (1a) and the non-racemic aziridinone (R)-1a (92percent e.e.) is studied in solution in the temperature range of 100-140 deg C.Besides traces of the imine 8, which is the product of a direct cycloreversion of 1a, the aldehyde 2a and the isocyanide 4a are formed in almost quantitative yield.A small fraction of the latter rearranges to the nitrile 3 or adds to unchanged 1a to afford the iminoazetidinone (E)-5a (5-10percent), which is obtained when neat 1a is heated in the presence of 4a.The configuration of (E)-5a is based on nuclear Overhauser experiments.The disappearance of 1a follows a first-order rate law with k = 44 * 10-6 s-1 at 130 deg C, while racemization of (R)-1a is observed with k (S)-1a> = 8.1 * 10-6 s-1.The formal cycloaddition of tert-butyl isocyanide (4a) to (R)-1a produces (E,R*)-5a of unknown absolute configuration and a low enantiomeric excess (ca.10percent).The product (E,R*)-5a is not racemized under the reaction conditions.The results are interpreted in terms of a nucleophilic attack of the isocyanide 4a to C-3 of (R)-1a resulting in an acyclic nitrilium type zwitterion (R)-21 which, to a large extent racemizes via the ketene imine 22 before ring-closure to the final product (E,R)-5a. - Dimethylformamide reacts with (R)-1a at temperatures as low as 80-100 deg C to give the diastereomeric oxazolidin-5-ones cis- and trans-15.The former is formed first and subsequently isomerizes to trans-15.The configuration of cis- and trans-15 is based on nuclear Overhauser experiments.The proton signals of the dimethylamino group of both cis- and trans-15 are temperature-dependent and split into two singlets of equal intensity at Tc = 271 and 250 K as a result of the retardation of two processes, viz. the N inversion and the rotation around the (C-NMe2) bond.In the reaction of (R)-1a with dimethylformamide, the oxazolidinones (2R,5S)- and (2S,5S)-15 (85-90percent e.e.) are formed which are hydrolyzed to the known α-hydroxyamide (S)-16.Hence, the configuration at C-5 of both cis- and trans-15 is (S), and the cycloaddition of (R)-1a to dimethylformamide involves inversion at C-3 of (R)-1a.This result strongly suggests a nucleophilic attack of dimethylformamide to (R)-1a rather than trapping of an acyclic aziridinone isomer. - In order to rationalize the observed reactions and reactivities, we performed high-level calculations on the parent aziridinone 29 and its cyclic (30, 31) and acyclic (32-35) isomers as well.Among the three-membered rings, 29 (MP2/6-31G*//6-31G*, Erel = 0.00 kJ mol-1) is lowest in energy, followed by the iminooxiranes (E)- and (Z)-31 (Erel = 30.8 and 26.0 kJ mol-1) and the methyleneoxaziridine 30 (Erel = 195.6 kJ mol1-).Energy-rich zwitter-ionic transition states (E)- and (Z)-32 (Erel = 281.9 and 234.6 kJ mol-1) are found the RHF method.The UHF method is used for open-shell species.Thus, UHF/6-31G*//6-31G* optimizations result in the planar triplet states 33 having very low relative energies, but high spin conta...
- Quast, Helmut,Leybach, Holger,Wuerthwein, Ernst-Ulrich
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p. 1249 - 1262
(2007/10/02)
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- Dithiazoles and Related Compounds. Part 3. Preparation of 5H-1,4,2-Dithiazoles via 1,3-Dipolar Cycloadditions between Nitrile Sulphides and Thiocarbonyl Compounds, and some Conversions into 3,5-Diaryl-1,4,2-dithiazolium Salts
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Thermolysis of 1,3,4-oxathiazol-2-ones 3 in the presence of thiocarbonyl compounds gives modest to good yields of the little-known 5H-1,4,2-dithiazoles 1, the reaction being successful with diaryl, aryl alkyl and dialkyl ketones, and thiono esters, but failing with dithio esters and tertiary thioamides.The influence of substituents is discussed.Solvolysis of 5-ethoxy-5H-1,4,2-dithiazoles, derived from thiono esters, with perchloric acid in acetic anhydride gives high yields of 3,5-diaryl-1,4,2-dithiazolium salts 9.
- Wai, Kwok-Fai,Sammes, Michael P.
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p. 183 - 187
(2007/10/02)
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Diazocompound 1 turns out to be the ideal photochemical precursor for tetrahedrane 3. Upon thermolysis Dewarpyridazine 6 is fragmented quantitatively into tri-tert-butylazete 8 and pivalonitrile 9.
- Maier, Guenther,Fleischer, Frank
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- Insertion, adduct formation, and elimination of alkenes in gas-phase reactions of bis(η5-cyclopentadienyl)methylzirconium(1+) with nitriles
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The gas-phase reactions of Cp2ZrCH3+, (1, Cp = cyclopentadienyl) with a number of alkyl nitriles and benzonitrile have been studied by using Fourier transform ion cyclotron resonance mass spectrometry. The formation of adducts occurs readily for all nitriles investigated, and the rate constants for adduct formation in the reaction of 1 with acetonitrile were determined. The rate constants range from 0.05kc-0.15kc as buffer gas pressures are increased from 0 to ~ 1.5 × 10-6 Torr, where kc is the estimated ion/molecule collision rate (2.2 × 10-9 cm3 s-1). Insertion of nitriles is proposed to yield azomethine complexes, and in several cases the reverse reaction, deinsertion, produces Cp2ZrR+ and N≡CCH3, where R is the alkyl or phenyl portion of the nitrile substrate. Comparisons of reactivity of the gas-phase ion 1 to solution chemistry are considered, since both adduct formation and insertion have been observed for d0fn complexes in solution. Reactions of 1 with n-alkyl nitriles having alkyl groups larger than methyl result in elimination of alkenes producing Cp2ZrN=C(H)(CH3)+, presumably by a mechanism involving deinsertion. Formation of Zr-allyl complexes is also observed for reaction of 1 with R-C≡N (R = propyl, butyl). Lower limits for relative Cp2Zr+-R bond disruption enthalpies are derived where possible and indicate that relative bond disruption enthalpies for Cp2Zr-R+ complexes are similar to those reported for related neutral complexes in solution. The reactivity of 1 with nitriles is comparable to reactivity of analogous neutral and cationic d0fn metal complexes, but additional reaction pathways are observed in the gas phase.
- Christ Jr., Charles S.,Eyler, John R.,Richardson, David E.
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p. 4778 - 4787
(2007/10/02)
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- Eine neue Methode zur Herstellung von Nitrilen aus Aldoximen
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Aldoximes are dehydrated to nitriles in good yields by reaction with methyl or ethyl cyanoformates.The method can also be used for the synthesis of tert-butyl cyanoformate from tert-butyl oximinoacetate.
- Thomas, H. G.,Greyn, H. D.
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p. 129 - 130
(2007/10/02)
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- Nucleophilic Substitution Reactions of Alkyl Halides By Using New Polymer-Supported Reagents Containing Hemin
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A new polymer reagent consisting of hemin, divinylbenzene, and 2-methyl-5-vinylpyridine was synthesized by suspension copolymerization.Substitution reactions of primary, secondary, and tertiary alkyl halides with the hemin copolymer combined with cyanide, azide, and thiocyanate ions were given satisfactory yields.This reaction mechanism was revealed to be a SNi type on the basis of stereochemical study.The hemin copolymer was not only a polymer-supported reagent with functional capabilities, but also served to separate the product from the reaction mixture.
- Saito, Kiyoshi,Harada, Kaoru
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p. 2562 - 2566
(2007/10/02)
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- Simple and Efficient Copper-Catalyzed One-Pot Conversion of Aldehydes into Nitriles
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Aromatic, heterocyclic, and tertiary aliphatic nitriles are prepared from the corresponding aldehydes by the ammonium chloride/copper powder/oxygen system in pyridine.This new one-flask procedure affords very high to quantitative yields of pure nitriles.
- Capdevielle, Patrice,Lavigne, Andre,Maumy, Michel
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p. 451 - 452
(2007/10/02)
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- The Isonitrile-Nitrile Rearrangement. A Reaction without a Structure-Reactivity Relationship
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Reproducible rates of isomerisation of aliphatic isonitriles to nitriles in solution can be measured by GLC or IR when free-radical inhibitors are added to suppress a competing radical chain reaction.The reactivities of 19 primary, secondary, tertiary, cyclic, bicyclic, bridgehead, benzyl, substituted-benzyl, α-carbomethoxymethyl, and triphenylmethyl isocyanides in this rearrangement reaction vary by only a factor of 67 in rate or by +/- 2 kcal mol-1 in ΔG(excit.).This is explained by a tight hypervalent three-membered cyclic transition state in agreement with a previous prediction by ab initio calculation.The slower rate of 9-triptycyl isocyanide is proposed to be due to steric hindrance by the three peri hydrogens.Aromatic isocyanides isomerize about 10 times faster independent of polar para substituents and bulky ortho substituents.A hypervalent orthogonal transition state with retention of the aromatic sextet is proposed in contrast to the popular phenonium-type transition states for aryl migration in other 1,2-rearrangements.The reactivity data and the transition-state structures are discussed in context with other cationotropic 1,2-shifts.
- Meier, Michael,Mueller, Barbara,Ruechardt, Christoph
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p. 648 - 652
(2007/10/02)
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- Anodic Oxidation of Alkyl Isocyanates and Their Thio Derivatives in Acetonitrile
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Seven alkyl isocyanates (RNCO), five alkyl isothiocyanates (RNCS), and two aromatic cyanato derivatives (ArNCO) were electrochemically investigated by cyclic voltammetry and anodic controlled-potential electrolysis in acetonitrile at platinum anodes.It was found that RNCS compounds exhibited considerably lower anodic potentials than RNCO derivatives.The preparative electrochemical oxidation of RNCS was dependent on the nature of the alkyl group.Primary RNCS afforded mainly five-membered heterocyclic products while tertiary ones gave largery amides due to α-cleavage or isocyanates due to substitution of sulfur for oxygen processes.RNCO compounds were oxidized at the onset of the solvent electrolyte region and yielded amides and carbonyl products due to nucleophilic involvement of either acetonitrile or water, respectively, or formed products due to radical reactions (mono-, di-, and tricyanomethyl derivatives).ArNCO gave mostly polymeric products.Mechanistic routes for the formation of the various products are discussed.
- Becker, James Y.,Zinger, Baruch,Yatziv, Shimon
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p. 2783 - 2789
(2007/10/02)
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- FACILE CONVERSION OF CARBOXAMIDES TO NITRILES
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Alkyl, aralkyl, aryl, heteroaryl carboxamides bearing various functionalities are readily converted to the corresponding nitriles in good yields using the liquid "diphosgene", trichloromethyl chloroformate, as dehydrating agent.In many cases, the procedure does not require extraction, and hence offers a very simple work-up.
- Mai, Khuong,Patil, Ghanshyam
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p. 2203 - 2206
(2007/10/02)
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- Trichloromethyl Carbonochloridate: A Dehydrating Reagent for the Preparation of Nitriles from Aldoximes
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Alkyl, aralkyl, and heteroaryl aldoximes bearing various functionalities are readily converted to the corresponding nitriles in good yields using trichloromethyl carbonochloridate as dehydrating agent.
- Mai, Khuong,Path, Ghanshyam
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p. 1037 - 1038
(2007/10/02)
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- Investigations on Diazo Compounds and Azides, XLIII. 1,2-Dewarpyridazines - Suitable Precursors for the Generation of Azacyclobutadienes?
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Heating of the (diazomethyl)cyclopropenes 9b and c yields the pyridazines 10b and c as main products.The formation of the carbenes 11b and c, which decompose into the acetylenes 12 and 13, competes with the isomerization reaction.The pyridazine 10d is obtained immediately by electrophilic diazoalkane substitution of 6 with the cyclopropenylium salt 8; 9d can be established as intermediate by IR spectroscopy.The irradiation of the pyridazines 10a-d (10a is described in literature) leads to the stable 1,2-Dewarpyridazines 15a-d.The flash pyrolysis of 15b, conducted exemplarily, affords the fragment pairs 16 and 13b as well as 12 and 20.Their formation is in agreement with the intermediacy of the valence tautomeric azacyclobutadienes 1718.
- Eisenbarth, Philipp,Regitz, Manfred
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p. 445 - 454
(2007/10/02)
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- The Mechanism of the Bischler-Napieralski Reaction, II: o-Chlorinated β-Phenethylamides as By-Products of the Ring Closure with PCl5
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In addition to 3,4-dihydroisoquinolines o-chloro-β-phenethylamides are formed in the Bischler-Napieralski reaction using PCl5.Possible mechanisms for the chlorination were tested in model experiments.
- Berger, Ulrich,Dannhardt, Gerd,Wiegrebe, Wolfgang
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p. 488 - 495
(2007/10/02)
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- A FREE RADICAL CHAIN MECHANISM FOR THE ISONITRILE - NITRILE REARRANGEMENT IN SOLUTION AND ITS INHIBITION.
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A large fraction of the isonitrile-nitrile rearrangement of t-alkyl isonitriles in solution follows a free radical chain mechanism of the addition-elimination type.
- Meier, Michael,Ruechardt, Christoph
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p. 4671 - 4674
(2007/10/02)
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