- A convenient synthesis of 2-oxazolines and 2-benoxazoles with PPh3-DDQ as the dehydrating reagent
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2-Oxazolines and 2-benoxazoles were synthesized in high yields from acylamino alcohols and acylaminophenols, respectively, with triphenylphosphine- 2,3-dichloro-5,6-dicyanobenzoquinone (PPh3-DDQ) as the dehydrating and activating reagent. The synthesis was accomplished under neutral conditions.
- Xu, Quancai,Li, Zhengning,Chen, Huiying
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Read Online
- Preparation of an improved sulfonated carbon-based solid acid as a novel, efficient, and reusable catalyst for chemoselective synthesis of 2-oxazolines and bis-oxazolines
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A highly sulfonated carbon as an efficient, recyclable, nontoxic, and green solid acid catalyst was readily synthesized by simultaneous sulfonation, dehydration, and carbonization of sucrose in sulfuric acid and was characterized by FT-IR, TG-DTG, XRD, and CHNS analysis, neutralization potentiometric titration, and SEM techniques. This new catalyst was used for preparation of 2-oxazolines and bis-oxazolines by reaction of β-aminoethanol with nitriles under reflux conditions. Sonication of this system enhanced the catalytic activity of the carbon-based solid acid and led to higher product yields and shorter reaction times. Another advantage of the system under ultrasonic irradiation is the ability to carry out large-scale reactions. In two cases, the catalyst was reused several times without loss of its activity.
- Mirkhani, Valiollah,Moghadam, Majid,Tangestaninejad, Shahram,Mohammadpoor-Baltork, Iraj,Mahdavi, Mohammad
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Read Online
- Direct oxidative conversion of aldehydes and alcohols to 2-imidazolines and 2-oxazolines using molecular iodine
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Aldehydes were converted to the corresponding 2-imidazolines and 2-oxazolines in good yields by the reaction with ethylenediamine and aminoethanol, respectively, using molecular iodine and potassium carbonate. Moreover, primary alcohols were directly converted to the corresponding 2-imidazolines and 2-oxazolines via aldehydes in one-pot manner with ethylenediamine and aminoethanol, respectively, using molecular iodine and potassium carbonate.
- Ishihara, Midori,Togo, Hideo
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Read Online
- Copper N-Heterocyclic Carbene Complexes As Active Catalysts for the Synthesis of 2-Substituted Oxazolines from Nitriles and Aminoalcohols
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The reaction between nitriles and aminoalcohols to access 2-substituted oxazolines was investigated. Using copper-NHC complexes, various nitriles were successfully converted into the corresponding oxazolines, under milder and less wasteful conditions than those of previously reported methods.
- Trose, Michael,Lazreg, Fa?ma,Lesieur, Mathieu,Cazin, Catherine S. J.
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Read Online
- A novel and chemoselective synthesis of 2-aryloxazolines and bis-oxazolines catalyzed by Bi(III) salts
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Different arylnitriles react with β-aminoalcohols in the presence of catalytic amounts of Bi(III) salts such as Bi(TFA)3, Bi(OTf) 3 and BiOClO4·XH2O producing the corresponding 2-aryl-oxazolines in high yields. Selective synthesis of mono- and bis-oxazolines from dicyanobenzenes and selective conversion of arylnitriles to their 2-oxazolines in the presence of alkylnitriles can be considered as noteworthy advantages of this method. Georg Thieme Verlag Stuttgart.
- Mohammadpoor-Baltork, Iraj,Khosropour, Ahmad Reza,Hojati, Seyedeh Fatemeh
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Read Online
- A convenient synthesis of oxazolines and imidazolines from aromatic aldehydes with pyridinium hydrobromide perbromide in water
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Various 2-oxazolines were prepared from aromatic aldehydes and 2-aminoethanol with pyridinium hydrobromide perbromide in water at room temperature. 2-Imidazolines were also obtained in good yields from aromatic aldehydes and ethylenediamine under the same reaction conditions. Georg Thieme Verlag Stuttgart.
- Sayama, Shinsei
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Read Online
- Rhodium(III)-Catalyzed Oxidative Cyclization of Oxazolines with Cyclopropanols: Synthesis of Isoindolinones
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The synthesis of C3-substituted isoindolin-1-ones from oxazolines and cyclopropanols has been achieved with oxazoline as a bifunctional nucleophilic directing group. The reaction proceeds by the cleavage of three chemical bonds and allows the formation of three new chemical bonds, a C-N bond, a C-C bond, and a C-O bond, in a single step.
- Liu, Jidan,Yang, Zhenke,Jiang, Jinyuan,Zeng, Qiaohai,Zheng, Liyao,Liu, Zhao-Qing
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Read Online
- A facile synthesis of 2-oxazolines using a PPh3-DDQ system
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A facile and efficient synthesis of 2-oxazolines from N-(2-hydroxyethyl)amides using a triphenylphosphine-2,3-dichloro-5,6-dicyanobenzoquinone (PPh3-DQQ) system is described. The reaction proceeds under neutral and mild conditions, and excellent yields are obtained.
- Xu, Quancai,Li, Zhengning
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Read Online
- Facile one-pot synthesis of 2-oxazoline
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We developed a facile one-pot synthesis of 2-oxazolines from carboxylic acid and 2-chloroethyl isocyanate, involving amide bond formation and a following intramolecular cyclization using 4-dimethylaminopyridine as the catalyst. A large variety of functional groups are well tolerated by the mild reaction conditions to afford diverse 2-oxazolines in good to excellent yields. This reaction will keep the chirality of the isocyanate at position 1, the R2 substituted carbon. Microwave-assisted synthesis can further enhance the reaction yield and reduce the reaction time to 5 min. This method facilities the synthesis of 2-oxazolines for diverse applications, such as 2-oxazoline derived polymers and materials.
- Zhu, Jipeng,Zhou, Min,Jiang, Weinan,Zhou, Yang,Song, Gonghua,Liu, Runhui
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supporting information
(2022/01/28)
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- Oxazolinyl-Assisted Ru(II)-Catalyzed C-H Allylation with Allyl Alcohols and Synthesis of 4-Methyleneisochroman-1-ones
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We report herein a ruthenium-catalyzed, oxazoline-directed strategy for C-H allylation of aryl oxazolines using allylic alcohols as the coupling partner. The present transformation unravels the unusual reactivity of allylic alcohols in the synthesis of 4-
- Singh, Diksha,Kumar, Gangam Srikanth,Kapur, Manmohan
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p. 12881 - 12892
(2019/09/30)
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- Oxazolinyl-Assisted Ru(II)-Catalyzed C?H Functionalization Based on Carbene Migratory Insertion: A One-Pot Three-Component Cascade Cyclization
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A rare, ruthenium-catalyzed, oxazolinlyl assisted C?H functionalization and three-component cascade cyclization for the synthesis of isoquinolinones via a metal-carbene migratory insertion is reported. The transformation is unique since it involves the fo
- Kumar, Gangam Srikanth,Khot, Nandkishor Prakash,Kapur, Manmohan
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supporting information
p. 73 - 78
(2018/12/11)
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- Mild, Selective Ru-Catalyzed Deuteration Using D2O as a Deuterium Source
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A method for the selective deuteration of polyfunctional organic molecules using catalytic amounts of [RuCl2(PPh3)3] and D2O as a deuterium source is presented. Through variation of additives like CuI, KOH, and various amounts of zinc powder, orthogonal chemoselectivities in the deuteration process are observed. Mechanistic investigation indicates the presence of different, defined Ru-complexes under the given specific conditions.
- Eisele, Pascal,Ullwer, Franziska,Scholz, Sven,Plietker, Bernd
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supporting information
p. 16550 - 16554
(2019/12/11)
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- Radical-mediated intramolecular β-C(sp3)-H amidation of alkylimidates: Facile synthesis of 1,2-amino alcohols
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A new radical-mediated intramolecular β-C(sp3)-H amidation reaction of O-alkyl trichloro- or arylimidates is reported. Various oxazolines were efficiently prepared from easily accessible alcohol starting materials. The trichloro-oxazoline products can be hydrolyzed under mild conditions to give valuable 1,2-amino alcohols. This amidation reaction exhibits a broad substrate scope and good functional group tolerance, and offers a powerful means for the C(sp3)-H functionalization of alcohols. Mechanistic studies suggest that a sequence of 1,5-HAT of an imidate radical, iodination and cyclization might be operative.
- Mou, Xue-Qing,Chen, Xiang-Yu,Chen, Gong,He, Gang
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supporting information
p. 515 - 518
(2018/01/19)
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- A 2 - aryl - 2 - oxazoline preparation method
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The invention discloses a 2-aryl-2-oxazoline preparation method and belongs to the field of chemistry. According to the method, an aryl-amide compound and 1,2-dichloroethane are reacted for synthesis, and the synthesis reaction is conducted under the alka
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Paragraph 0007; 0013; 0014
(2017/06/21)
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- A 2 - substituted oxazoline or 2 - substituted piperazine synthetic method (by machine translation)
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The invention discloses a method for synthesizing 2 - substituted oxazoline or 2 - substituted oxazine new method, by nitrile and amino ethanol or 3 - amino - 1 - propanol as raw material, in the absence of solvent, can be used for the recycling of the sulfur to induce synthesis of 2 - substituted oxazoline and 2 - substituted piperazine. The method of the invention has low cost, simple reaction process, mild reaction conditions, the reaction time is short, the yield and the like, is suitable for the industrial generation. (by machine translation)
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Paragraph 0021; 0034
(2017/08/25)
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- Highly efficient synthesis of β-nitrate ester carboxamides through the ring-opening of 2-oxazolines
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A novel method for the synthesis of β-nitrate ester carboxamides using non-corrosive tert-butyl nitrite (TBN) as the nitro source and easily available oxygen as the oxidant has been developed. Variously substituted 2-oxazolines were efficiently ring-opened to deliver the corresponding products in excellent yields. Notably, this reaction provides fast access to pharmaceuticals such as nicorandil.
- Qiao, Kai,Yuan, Xin,Wan, Li,Zheng, Ming-Wei,Zhang, Dong,Fan, Bing-Bing,Di, Zhe-Chen,Fang, Zheng,Guo, Kai
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supporting information
p. 5789 - 5793
(2017/12/26)
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- Microwave-Assisted Synthesis of 2-Aryl-2-oxazolines, 5,6-Dihydro-4H-1,3-oxazines, and 4,5,6,7-Tetrahydro-1,3-oxazepines
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The first general procedure for the synthesis of 5- to 7-membered cyclic iminoethers by microwave-assisted cyclization of ω-amido alcohols promoted by polyphosphoric acid (PPA) esters is presented. 2-Aryl-2-oxazolines and 5,6-dihydro-4H-1,3-oxazines were efficiently prepared using ethyl polyphosphate/CHCl3. Trimethylsilyl polyphosphate in solvent-free conditions allowed for the synthesis of hitherto-unreported 4,5,6,7-tetrahydro-1,3-oxazepines. The method involves good to excellent yields and short reaction times.The reaction mechanism and the role of PPA esters were investigated in a chiral substrate.
- Mollo, María C.,Orelli, Liliana R.
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p. 6116 - 6119
(2016/12/09)
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- A Mild and Regioselective Route to Functionalized Quinazolines
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A Rh-catalyzed ortho-amidation cyclocondensation sequence gave a range of 4-aminoquinazolines in high yield. The method features a remarkably mild C(sp2)-H activation step and can be exploited to rapidly access compounds with established biological activity.
- Maiden, Tracy M. M.,Swanson, Stephen,Procopiou, Panayiotis A.,Harrity, Joseph P. A.
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p. 14342 - 14346
(2015/10/05)
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- An efficient one-pot synthesis of 2-oxazolines with molecular iodine under ultrasound irradiation
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A series of 2-oxazolines were prepared by the condensation of aldehydes with 2-aminoethanol in the presence of molecular iodine and potassium carbonate in t-BuOH at 35-40 °C under ultrasound irradiation. The easy work-up procedure and moderate to good yie
- Xiao, Nan,Wang, Sen Hao,Zhang, Ai Ying,Li, Hong Yang,Wang, Peng,Li, Wei,Chen, Bao Hua,Chen, Guo Feng,Li, Na
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p. 9731 - 9742
(2016/01/12)
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- Ruthenium(II) 9,10-phenanthrenequinone thiosemicarbazone complexes: Synthesis, characterization, and catalytic activity towards the reduction as well as condensation of nitriles
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The ligands 9,10-phenanthrenequinone-N4-substituted thiosemicarbazones (HL1-3) and their ruthenium(II) complexes were synthesized and characterized by elemental and spectroscopic methods. The ligands are tridentate, monobasic chelating ligands with O, N, and S as the donor sites and are in the thiol form in all the complexes. Catalytic studies showed that all the complexes displayed good catalytic activity towards the reduction of nitriles and also the condensation of nitriles with 2-aminoalcohol under solvent-free conditions.
- Anitha, Panneerselvam,Viswanathamurthi, Periasamy,Kesavan, Devarayan,Butcher, Ray Jay
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p. 321 - 334
(2015/10/20)
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- Ruthenium(II) 8-quinolinolates: Synthesis, characterization, crystal structure and catalysis in the synthesis of 2-oxazolines
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Abstract New octahedral ruthenium(II) complexes (1-4) have been synthesized from the reaction of ruthenium(II) precursors [RuHCl(CO)(EPh3)3] (E = P or As) with the bidentate Schiff base ligands, 2-((2,6-dimethylphenylimino)methyl)quinolin-8-ol (L1) and 2-((2,6-diisopropylphenylimino)methyl)quinolin-8-ol (L2) in ethanol. These complexes have been characterized by elemental analyses, IR, UV-Vis, 1H, 13C and 31P NMR and ESI-Mass spectroscopy. The molecular structure of the complex [RuCl(CO)(PPh3)2(L2)] (2) was determined by single-crystal X-ray diffraction, which reveals a distorted octahedral geometry around ruthenium(II) ion. The catalytic activity of the new complexes was evaluated for the condensation of nitriles with ethanolamine under solvent free conditions. The processes were operative with aromatic and heteroaromatic nitriles and tolerated several substitutional groups. The studies on the effect of substitution over ligands, coligands, reaction time, temperature and catalyst loading were carried out in order to find the best catalyst in this series of complexes and favorable reaction conditions. A probable mechanism for the catalytic condensation of nitrile has also been proposed. The catalyst was recovered and recycled up to five times without significant loss of its activity.
- Anitha,Manikandan,Prakash,Pachiyappan,Viswanathamurthi,Malecki
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p. 266 - 273
(2015/06/22)
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- Polynuclear copper(ii) pyrazolate complexes: Temperature-dependent protonolysis reactions, crystal structures and high catalytic activity toward the condensation of nitriles with 2-aminoalcohol
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Reaction of Cu(OAc)2·H2O and 1H-pyrazole-3,5-dicarboxylic acid dimethyl ester (Hdcmpz) in MeOH at room temperature afforded one tetranuclear Cu(ii)/pyrazolate complex [{Cu 2(μ-OAc)2}2(μ-dcmpz)2/
- Wang, Ling,Guo, Bin,Li, Hong-Xi,Li, Qi,Li, Hai-Yan,Lang, Jian-Ping
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p. 15570 - 15580
(2013/11/06)
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- S-Co(II) cascade catalysis: Cyclocondensation of aromatic nitriles with alkamine
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A solvent-free S/Co(NO3)2 cascade catalyzed cyclocondensation reaction of aromatic nitriles with 3-amino-1-propanol or 2-aminoethanol has been successfully developed under thermal and microwave conditions. By this two-component protocol, mono- and bis-oxazines and oxazolines were selectively synthesized both in good to excellent yields and short reaction times. This catalytic system exhibits excellent chemoselectivity, and can be reused at least seven times without significant loss of activity in subsequent reactions.
- Ge, Haixia,Liu, Ping,Li, Xiangnan,Sun, Wei,Li, Jianli,Yang, Bingqin,Shi, Zhen
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p. 6591 - 6597
(2013/07/26)
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- DDQ-induced dehydrogenation of heterocycles for c-c double bond formation: Synthesis of 2-thiazoles and 2-oxazoles
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Strong as an Ox: 2-Thiazoles and 2-oxazoles are formed by oxidation of 2-thiazolines and 2-oxazolines without requiring substituents at the C4 and C5 positions. DDQ plays an important role as the oxidant in this transformation and metal is unnecessary. This general procedure shows good functional group tolerance and provides a wide variety of 2-thiazoles and 2-oxazoles in moderate to excellent yields.
- Li, Xiangnan,Li, Cheng,Yin, Bing,Li, Cong,Liu, Ping,Li, Jianli,Shi, Zhen
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supporting information
p. 1408 - 1411
(2013/07/26)
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- Solvent-free tandem synthesis of 2-thiazolines and 2-oxazolines catalyzed by a copper catalyst
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Tandem reactions of nitriles with 2-aminoethanethiol hydrochloride or amino alcohols in the presence of a catalytic amount of cupric methacrylate (Cu II2L4, L = methacrylate) were employed to prepare 2-thiazolines and 2-ox
- Li, Xiangnan,Zhou, Baoyue,Zhang, Jin,She, Mengyao,An, Shujuan,Ge, Haixia,Li, Cong,Yin, Bing,Li, Jianli,Shi, Zhen
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experimental part
p. 1626 - 1632
(2012/05/04)
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- Poly(N-bromo-N-ethyl-benzene-1,3-disulfonamide), N,N,N′,N′- tetrabromobenzene-1, 3-disulfonamide as new efficient reagents for conversion of alcohols to THP ethers and aldehydes to oxazoline compounds
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This paper is concerned with an easy preparation of THP ethers from primary, secondary and tertiary alcohols and oxazoline compounds from various aldehydes using poly(N-bromo-N-ethyl-benzene-1,3-disulfonamide), N,N,N′,N′-tetrabromobenzene-1,3-disulfonamide [TBBDA] as new and efficient reagents under ambient conditions without over-oxidation.
- Ghorbani-Vaghei,Akbari-Dadamahaleh,Amiri
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experimental part
p. 301 - 307
(2010/09/03)
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- An efficient oxidative conversion of aldehydes into 2-substituted 2-oxazolines using 1,3-diiodo-5,5-dimethylhydantoin
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Various aromatic and aliphatic aldehydes were converted into the corresponding 2-aryl and 2-alkyl-2-oxazolines, respectively, in good to high yields by reaction with 2-aminoethanol and 1,3-diiodo-5,5-dimethylhydantoin. Moreover, chiral bis-2-oxazolines, which can be used as chiral ligands in asymmetric synthesis, could be also prepared in moderate yields by the reaction of dialdehydes with (R)-(-)-2-phenylglycinol under the same conditions. Georg Thieme Verlag Stuttgart.
- Takahashi, Shogo,Togo, Hideo
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experimental part
p. 2329 - 2332
(2010/03/01)
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- Practical reduction of oxazolines to alcohols
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A two-step, one-pot procedure using methyl chloroformate and lithium borohydride was developed to transform 2-substituted-oxazolines into alcohols. This methodology is compatible with a wide range of substrates including heterocyclic, aromatic, and aliphatic functionalized 2-oxazolines. Best results are obtained with electron-rich and ortho substituted 2-aryl-oxazolines.
- Bernardi, Anna,Ouellet, Stéphane G.,Angelaud, Remy,O'Shea, Paul D.
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supporting information; experimental part
p. 6707 - 6708
(2009/04/07)
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- Efficient oxidative conversion of aldehydes to 2-substituted oxazolines and oxazines using (diacetoxyiodo)benzene
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An efficient synthesis of 2-substituted oxazolines from aldehydes and 2-amino alcohol using (diacetoxyiodo)benzene as an oxidant, is reported. (Diacetoxyiodo)benzene acts as a mild dehydrogenating agent to convert the initially formed oxazolidine from ald
- Karade, Nandkishor N.,Tiwari, Girdharilal B.,Gampawar, Sumit V.
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p. 1921 - 1924
(2008/03/27)
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- Synthesis of 2-oxazolines and 2-thiazolines using lanthanide amino alkoxide
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New 2-oxazolines and 2-thiazolines are prepared from phenacysulfonylacetic acid methyl ester using lanthanide amino alkoxide. Copyright Taylor & Francis Group, LLC.
- Padmavathi,Reddy, B. Chandra Obula,Thriveni,Mohan, A.V. Nagendra
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p. 3127 - 3142
(2008/02/13)
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- NOVEL METHODS FOR THE TREATMENT OF INFLAMMATORY DISEASES
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Methods of inhibiting the cytokine or biological activity of Macrophage Migration Inhibitory Factor (MIF) comprising contacting MIF with a compound of formula (I) are provided. The invention also relates to methods of treating diseases or conditions where MIF cytokine or biological activity is implicated comprising administration of compounds of formula (I), either alone or as a part of combination therapy. Novel compounds of formula (I) are also provided for.
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- A simple synthesis of 2-substituted oxazolines and oxazines
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β-Aminoalcohols react with carboxylic acids in the presence of a zeolite, Ersorb-4, resulting in the formation of oxazoline derivatives in good yields. Similarly, 3-aminopropanol and benzoic acid gave the corresponding 2-phenyloxazine.
- Cwik, Agnieszka,Hell, Zoltán,Hegedüs, Adrienn,Finta, Zoltán,Horváth, Zoltán
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p. 3985 - 3987
(2007/10/03)
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- Medical use of fluorenone derivatives for treating and preventing brain and spinal injury
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Newly-created fluorenone drugs can be used to prevent, treat, or otherwise reduce damage to a brain or spinal cord following a medical crisis. These new drugs are markedly improved analogs of previously-known fluorenone compounds that were never commercialized or developed into medically useful treatments. The new analogs have the following structure: STR1where X is a lower alkyl, substituted alkyl, or cycloalkyl group, R is selected from certain types of ether, ester, or amide groups, and Y 1 and Y 2 are halogen, hydrogen, or methyl. These new compounds can penetrate a blood-brain barrier and potently inhibit the unwanted release of excitotoxic neurotransmitters by astrocyte cells following an injury or insult to the brain or spinal cord. As an illustration, some of these new analogs were more than 30 times more potent than the previously known best compound in reducing aspartate release by stressed astrocytes. The new analogs also reduce swelling in astrocytes, thereby promoting proper blood flow through the brain and spinal cord following an injury or other crisis. These new analogs have been shown to work with very good efficacy in in vivo animal models of focal or global brain ischemia.
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- 1H NMR spectroscopic investigation of the mechanism of 2-substituted-2- oxazoline ring formation and of the hydrolysis of the corresponding oxazolinium salts
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Chlorination of 2-hydroxyethylamides containing electrondonor substituents such as alkyl, phenyl or alkyl- or alkyloxy-substituted phenyl at 23 °C with SOCl2 proceeds via 2-substituted-2-oxazolinium hydrochlorides that can be transformed in sit
- Holerca, Marian N.,Percec, Virgil
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p. 2257 - 2263
(2007/10/03)
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- Efficient Cyclodesulfurization of N-(2-Hydroxyethyl)-N′-Arylthioureas to Δ2-Oxazolines Using Superoxide Radical Anion
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Δ2-Oxazolines have been synthesized in good yields by the cyclodesulfurization of N-(2-hydroxyethyl)-N′-phenylthioureas with superoxide radical anion (O2-?) at room temperature in anhydrous acetonitrile.
- Kim, Yong Il,Kim, Yong Hae
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p. 1324 - 1326
(2007/10/03)
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- Reactions of N-Benzyl- and N-Benzylidene-alkanolamines with Bromine: Formation of 1,3-Oxazolidines, 1,3-Oxazinanes, 4,5-Dihydro-1,3-oxazoles and 5,6-Dihydro-4H-1,3-oxazines
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N-Methylbenzylamines react with bromine in acetonitrile to form N-benzylidenemethylamines.Under similar conditions 2-benzylaminoethanols and 3-benzylaminopropan-1-ols afford 3-benzyl-2-phenyl-1,3-oxazolidines and 3-benzyl-2-phenyl-1,3-oxazinanes, respectively. 2-Benzylidineaminoethanols and 3-benzylideneaminopropan-1-ols likewise give 2-aryl-4,5-dihydro-1,3-oxazoles and 2-aryl-5,6-dihydro-4H-1,3-oxazines, respectively.When N-benzylidenemethylamine is treated with bromine in the presence of alcohols, benzaldehyde acetals are obtained.
- Goosen, Andre,McCleland, Cedric W.,Sipamla, Allworth M.
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p. 2221 - 2232
(2007/10/03)
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- Synthesis of Δ2-1,3-oxazolines from cationic platinum(II) nitrile complexes. X-ray structure of trans-[Pt(CF3){N=C(Ph)OCH2CH2}(PPh 3)2]BF4·0.5H 2O·0.25MeOH
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Cationic Pt(II) nitrile complexes of the type trans-[Pt(R′)(NCR)(PPh3)2]BF4 (R′ = H (1), CH3 (2), R = CH3; R′ = CF3, R = CH3 (3), CH3CH2 (4), CH3CH2CH2 (5), (CH3)2CH (6), (CH3)3C (7), C6H5 (8), p-CH3C6H4 (9), o-CH3C6H4 (10), p-OCH3C6H4 (11)) have been prepared by reaction of the corresponding halo complexes trans-[Pt(R′)X(PPh3)2] (X = Cl, Br) with AgBF4 in the presence of a 20-30-fold excess of RCN in CH2Cl2. The complexes 1-11 readily react in THF at 0°C or below with HOCH2CH2Cl/n-BuLi (n-BuLi:complex molar ratio 1:1) to give a mixture of products, including the oxazoline complexes trans-[Pt(R′){N=C(R)OCH2CH2}(PPh3) 2]BF4 (1a-11a), the chloro complexes trans-[Pt(Cl(R′)(PPh3)2, and free oxazoline N=C(R)OCH2CH2. For short reaction times (ca. 10-15 min) the oxazoline complexes 1a-11a could be isolated albeit in modest yield (26-49%) from the reaction mixtures and they could be separated from the corresponding chloro complexes (average yield ca. 35%) by taking advantage of the higher solubilty of the latter derivatives in benzene. For longer reaction times (>2 h), the trans-[PtCl(R′)(PPh3)2] species were the only isolated products. Compounds 1a-11a have been characterized by IR and multinuclear (1H, 19F, 31P{1H}, and 13C{1H}) NMR spectroscopies and also by an X-ray structural determination, which has been carried out for 3a. It crystallizes in the orthorhombic space group Pna21, with a = 19.130(4) A?, b = 15.936(3) A?, c = 16.312(3) A?, V = 4973(2) A?3, and Z = 4. The structure was refined to R = 0.056 (Rw = 0.065) for 2485 measured reflections with I ≥ 3σ(I). The 2-(phenyl)oxazoline ligand is almost planar and perpendicular to the mean coordination plane. A mechanism is proposed for the conversion of nitriles to 2-oxazolines in cationic Pt(II) complexes. The reactions of the isolated complexes trans-[Pt(CF3){N=C(R)OCH2CH2}(PPh 3)2]BF4 (3a-11a) with excess chloride ions gave trans-[Pt(CF3)Cl(PPh3)2] and the corresponding free oxazolines, which were characterized by IR, 1H NMR, and GC/MS techniques. Attempts to generate catalytically 2-(methyl)oxazoline have been performed using the trans-[PtX(R)(PR3)2]/CH3CN/OCH 2CH2 system (PR3 = PEt3, PMe2Ph; R = H, CH3, CF3; X = Br, I). No oxazoline formation was observed between 50 and 75°C and 36 and 160 h; however, addition of LiBr and OCH2CH2 to trans-[PtBr(CH3)(PEt3)2] and trans-[PtBr(CF3)(PMe2Ph)2] (salt:complex (1.5-3):1 molar ratio) led to the formation of 2-(methyl)oxazoline, albeit not catalytically.
- Michelin, Rino A.,Mozzon, Mirto,Berin, Paola,Bertani, Roberta,Benetollo, Franco,Bombieri, Gabriella,Angelici, Robert J.
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p. 1341 - 1350
(2008/10/08)
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- N-Nitroso Compounds. Part 1. Structure and Decomposition of N-Nitroso-2-arylimidazolines in Aqueous Acidic Media
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Kinetic measurements for the acid-catalysed decomposition of N-nitroso-2-arylimidazolines are reported.Reactions are first-order in both +>.Two products are formed; an oxazoline, which is the product of hydrolysis of the amidine moiety, and the parent imidazoline formed by denitrosation of the substrate.These products arise from two competing pathways both of which are acid catalysed.The solvent isotope effects for the denitrosation, and amidine hydrolysis, , are 3.1 and 3.5, respectively.The denitrosation pathway, but not amidine hydrolysis, is catalysed by nucleophilic anions, and a value of 1.7 for the Swain-Scott constant, s, is obtained.In the abscence of nucleophilic anions, amidine hydrolysis is preferred over denitrosation, being twice as large as at 25 deg C.Substituents in the 2-aryl ring affect the rate of decomposition giving Hammett ρ values of 0.7 for denitrosation and 1.0 for amidine hydrolysis, which reflect the proximity of the reacting centres to the substituents.Values of the activation parameters are ΔH*NO 74 kJ/mol, ΔH*A 74 kJ/mol, ΔS*NO -48 J/K*mol and ΔS*A -43 J/K*mol.The data are interpreted in terms of a fast equilibrium protonation of the substrate, followed by competitive attack at the protonated substrate, either of water or nucleophilic anions at the nitroso nitrogen atom, or of water at the amidine carbon atom.Protonation is required to activate the substrate, the substrate being recovered from neutral or alkaline solutions unchanged.The mechanism is discussed with reference to the analogous reactions of N-nitrosoamines and N-nitrosoamides.
- Iley, Jim,Norberto, Fatima,Rosa, Eduarda
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p. 1471 - 1476
(2007/10/02)
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- The Use of 2-Oxazolidinone as a Latent Aziridine Equivalent. I. A Facile Method for the Preparation of 2-Substituted Oxazolines
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Ring-opening reaction of 2-oxazolidinone with acid chlorides followed by treatment with aqueous sodium hydroxide yields 2-substituted oxazolines.
- Poindexter, Graham S.
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p. 1431 - 1433
(2007/10/02)
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- TRANSFORMATIONS OF PYRIDINIUMS DERIVED FROM AMINO-ALCOHOLS AND FROM DIAMINES
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Pyridiniums derived from amino alcohols cyclise to ethers or rearrange to aldehydes on heating.Monopyridiniums from diamines can be acylated or converted into ureas or thioureas: these products cyclise on heating in solution to give dihydro-thiazoles, -4H-thiazines, -oxazoles, -4H-oxazines, or tetrahydro-3H-thiazepines.
- Katritzky, Alan R.,Langthorne, Roland T.,Patel, Ranjan C.,Lhommet, Gerard
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p. 2383 - 2390
(2007/10/02)
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