- Metal-Free Cascade Annulation Approach for Modular Assembly of Alkynyl/Benzoyl Functionalized Quinolines
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A concise and efficient synthetic method for alkynyl quinolines through TfOH-promoted cascade 1,4-conjugate addition/intramolecular annulation/aromatization process is established. By virtue of reactive aza-o-AQM (in situ generated from modular propargylamine), this reaction proceeds smoothly to afford a variety of alkynyl quinolines in good to excellent yields. This transition-metal-free process features halogen groups tolerance, such as the ?Cl, ?Br, and ?I groups; thus, this protocol circumvents the inherent shortcomings of the existing Sonogashira coupling of halogenated quinolines.
- Tang, Qiang,Yuan, Meng,Duan, Jiahui,Xu, Keke,Li, Ruxue,Xie, Mengqing,Kong, Shuwen,He, Xinwei,Shang, Yongjia
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supporting information
(2022/01/19)
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- Iodine-Promoted Formal [3+2] Cycloaddition of Enaminone: Access to 2-Hydroxy-1,2-dihydro-pyrrol-3-ones with Quaternary Carbon Center
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A novel iodine promoted cyclization of enaminone with aryl methyl ketones has been developed as a straightforward method for constructing 2-hydroxy-pyrrol-3(2H)-ones. This strategy affords structurally diverse 2-hydroxy-pyrrol-3(2H)-ones rings in high yields. Moreover, a quarternary alcohol has been constructed efficiently in the reaction. Product purification required only washing with CH2Cl2 solvent, thereby avoiding traditional chromatography and recrystallization, making this an example of group-assisted purification chemistry.
- Yu, Xiao-Xiao,Zhao, Peng,Zhou, You,Huang, Chun,Wang, Li-Sheng,Wu, Yan-Dong,Wu, An-Xin
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p. 12141 - 12147
(2021/09/07)
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- Copper-Catalyzed Reductive Ring-Cleavage of Isoxazoles: Synthesis of Fluoroalkylated Enaminones and Application for the Preparation of Celecoxib, Deracoxib, and Mavacoxib
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We have identified a new reactivity of copper/diamine catalysis for the reductive ring-cleavage of isoxazoles to yield fluoroalkylated enaminones. This protocol has the advantage of using commercially available reagents, ease of setting up, broad tolerance of functionality, and is regiospecific and free of defluorination and reduction of reducible functional groups. The utility was demonstrated by a one-step, regioselective synthesis of fluoroalkylated pyrazole-based drugs such as celecoxib, deracoxib, and mavacoxib.
- Wan, Chao,Pang, Jian-Yu,Jiang, Wei,Zhang, Xiao-Wei,Hu, Xiang-Guo
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p. 4557 - 4566
(2021/03/01)
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- Unusual Reactivity of 4-Vinyl Isoxazoles in the Copper-Mediated Synthesis of Pyridines, Employing DMSO as a One-Carbon Surrogate
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An efficient protocol for the synthesis of nicotinate derivatives and tetrasubstituted pyridines through a copper-mediated cleavage of isoxazoles has been developed. The highlight of the work is the observation of an unusual reactivity of 4-vinyl isoxazoles under the reaction conditions. DMSO serves as a one-carbon surrogate generating an active methylene group during the reaction to form two C-C bonds. This protocol provides a facile and an expeditious approach for the assembly of densely substituted N-heterocyclic compounds.
- Kumar, Pravin,Kapur, Manmohan
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supporting information
p. 5855 - 5860
(2020/07/30)
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- Synthesis of new fluorescent molecules having an aggregation-induced emission property derived from 4-fluoroisoxazoles
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Fluorescent molecules based on a fluorinated isoxazole scaffold were synthesized and investigated for their photochemical properties. The introduction of a fluorine substituent into 3,5-diarylisoxazoles led to an increase of fluorescence intensity and exh
- Karuo, Yukiko,Kawai, Kentaro,Kawasaki, Akira,Omote, Masaaki,Sato, Kazuyuki,Tarui, Atsushi
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supporting information
p. 1411 - 1417
(2020/07/08)
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- Synthesis of Thiazoles and Isothiazoles via Three-Component Reaction of Enaminoesters, Sulfur, and Bromodifluoroacetamides/Esters
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A three-component strategy for the synthesis of thiazoles and isothiazoles has been developed by employing enaminoesters, fluorodibromoiamides/ester, and sulfur. The thiazoles and isothiazoles were formed via two C-F bond cleavages along with the formation of new C-S, C-N, and N-S bonds. The strategy provides high selectivity for the synthesis of thiazoles/isothiazoles, which have vital applications in drug discovery and development.
- Ma, Xingxing,Yu, Xiaoxia,Huang, Hua,Zhou, Yao,Song, Qiuling
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supporting information
p. 5284 - 5288
(2020/07/14)
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- Selective Dehydrogenative Acylation of Enamides with Aldehydes Leading to Valuable β-Ketoenamides
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We have presented a unique example of dehydrogenative acylation of enamides with aldehydes enabled by an earth-abundant iron catalyst. The protocol provides the straightforward access to valuable β-ketoenamides with ample substrate scope and excellent functional group tolerance. Notably, distinct C-H acylation of enamide rather than at N-H moiety site occurs with absolute Z-selectivity was observed. Late-stage modifications of complex molecules and versatile synthetic utility of β-ketoenamides further highlight the practicability of this transformation.
- Liu, Rui-Hua,Shen, Zhen-Yao,Wang, Cong,Loh, Teck-Peng,Hu, Xu-Hong
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supporting information
p. 944 - 949
(2020/02/15)
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- Trisulfur-Radical-Anion-Triggered C(sp2)-H Amination of Electron-Deficient Alkenes
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A trisulfur-radical-anion (S3˙-)-triggered C(sp2)-H amination of α,β-unsaturated carbonyl derivatives with simple amines has been demonstrated. This protocol provides convenient access to a variety of synthetically valuable N-unprotected and secondary β-enaminones with absolute Z selectivity and tertiary β-enaminones with E selectivity. Mechanistic probe and electronic structure theory calculations suggest that S3˙- initiates the nucleophilic attacks via a thiirane intermediate.
- Nguyen, Khang X.,Nguyen, Thao T.,Nguyen, Tung T.,Pham, Hoai T. B.,Pham, Phuc H.,Phan, Nam T. S.,Wang, Haobin,Yang, Chou-Hsun
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supporting information
p. 9751 - 9756
(2020/12/21)
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- Asymmetric Aza-Diels-Alder Reactions of in Situ Generated β,β-Disubstituted α,β-Unsaturated N-H Ketimines Catalyzed by Chiral Phosphoric Acids
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A novel asymmetric synthesis of dihydropyridinones with vicinal quaternary stereocenters has been realized by asymmetric aza-Diels-Alder reactions of 3-amido allylic alcohols with oxazolones enabled by chiral phosphoric acid catalysis. A series of aryl/alkyl- and alkyl/alkyl-disubstituted 3-amido allylic tertiary alcohols and 4-substituted oxazolones could be well tolerated in these reactions, producing dihydropyridinones with excellent diastereoselectivities and high enantioselectivities. Mechanistic study and control experiments were performed to shed light on the reaction mechanism, in which a configurationally defined β,β-disubstituted α,β-unsaturated N-H ketimine was proposed as the key intermediate.
- He, Shunlong,Gu, Huanchao,He, Yu-Peng,Yang, Xiaoyu
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supporting information
p. 5633 - 5639
(2020/07/14)
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- Tris(β-ketoiminato)ruthenium(III) complexes: Electrochemical and computational chemistry study
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The electronic and electrochemical properties are reported here for the first time for a series of five tris(β-ketoiminato)ruthenium(III) complexes. Since the β-ketoiminato ligand is unsymmetrical, both fac and mer isomers are theoretically possible for t
- Ngake, Tankiso Lawrence,Potgieter, Johannes H.,Conradie, Jeanet
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- Cu-Catalyzed Denitrogenative Transannulation of 3-Aminoindazoles to Assemble 1-Aminoisoquinolines and 3-Aminobenzothiophenes
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We disclose a novel Cu-catalyzed denitrogenative transannulation of 3-aminoindazoles to afford diverse functionalized 3-aminobenzothiophenes and 1-aminoisoquinolines, in which denitrogenative transannulation of 3-aminoindazoles is reported for the first t
- Zhou, Yao,Wang, Ya,Lou, Yixian,Song, Qiuling
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supporting information
p. 8869 - 8873
(2019/09/12)
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- Electrochemical synthesis of enaminones: Via a decarboxylative coupling reaction
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An environmentally benign and efficient electrochemical synthesis of enaminones via a decarboxylative coupling reaction of α-keto acids using n-Bu4NI as a redox catalyst and electrolyte under constant current electrolysis in an undivided cell is reported. A broad vinyl azide substrate scope and high functional group tolerance are observed. A gram-scale reaction further demonstrates the practicability of the protocol. The results of cyclic voltammetry and control experiments indicate that I2 is likely the active species to initiate the oxidative decarboxylation via an acyl hypoiodite intermediate.
- Kong, Xianqiang,Liu, Yulong,Lin, Long,Chen, Qianjin,Xu, Bo
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supporting information
p. 3796 - 3801
(2019/07/31)
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- Metal-Free Method for Direct Synthesis of Functionalized β-Ketoenamines
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A new method for direct synthesis of β-ketoenamines was developed by a BF3·OEt2-catalyzed cyclization of 1-iodoalkyne and α-keto acid followed by an amine-mediated ring-opening in one pot. Its metal-free conditions allowed the easy synthesis of those products bearing the transition metal-sensitive functional groups. Its three-component process achieved wide range of functionalized products.
- Zeng, Xiaobao,Liu, Chulong,Yang, Weiguang,Weng, Yunxiang,Wang, Xinyan,Hu, Yuefei
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p. 3656 - 3661
(2019/03/20)
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- Catalyst control in positional-selective C-H alkenylation of isoxazoles and a ruthenium-mediated assembly of trisubstituted pyrroles
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High levels of catalyst control are demonstrated in determining the positional selectivity in C-H alkenylation of isoxazoles. A cationic rhodium-mediated, strong-directing group promotes C(sp2)-H activation at the proximal aryl ring whereas, the palladium-mediated electrophilic metallation leads to the C(sp2)-H activation at the distal position of the directing group. Synthetic elaboration of this C-H alkenylation product via ruthenium and copper co-catalysis leads to an efficient method for the assembly of densely substituted pyrroles.
- Kumar, Pravin,Kapur, Manmohan
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p. 2134 - 2138
(2019/03/26)
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- A new route to triphenylpyridines utilizing ketoximes as building blocks via cascade reactions under iron-organic framework catalysis
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Iron-based metal–organic framework VNU-20 was utilized as a heterogeneous catalyst for cascade reactions between ketoximes and dibenzyl ether to produce 2,4,6-triphenylpyridines. Additionally, benzyl alcohol and (dimethoxymethyl)benzene could be used as an alternative starting materials for the transformation. The oxidant exhibited a remarkable impact on the reactions, and di-tert-butylperoxide was the most appropriate candidate. The VNU-20 displayed higher efficiency than many homogeneous and heterogeneous catalysts. The catalyst was reusable for the cascade reactions without a noticeable deterioration in catalytic activity. This transformation is new, and would offer alternative routes to triphenylpyridines utilizing ketoximes as building blocks.
- Nguyen, Vu H.H.,Doan, Son H.,Van, Tram T.,Pham, Phuc H.,Nguyen, Tran T.N.,Nguyen, Ngoc N.,Tu, Thach N.,Phan, Nam T.S.
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- PhIO/Et3N ? 3HF-Mediated Formation of Fluorinated 2H-Azirines via Domino Fluorination/Azirination Reaction of Enamines
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A variety of enamine carboxylic esters and enaminones were converted to the biologically interesting fluorinated 2H-azirines through reactions with PhIF2 generated in situ by PhIO and Et3N ? 3HF in 1,2-dichroloethane, which features the hypervalent iodine reagents-mediated introduction of fluorine atom and formation of the 2H-azirine skeleton under metal-free conditions. The domino reaction is postulated to proceed via a PhIF2-mediated oxidative fluorination and a subsequent azirination of the fluorinated enamine intermediates. (Figure presented.).
- Zhang, Yong,Zhao, Xiaoyuan,Zhuang, Chen,Wang, Senlin,Zhang-Negrerie, Daisy,Du, Yunfei
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supporting information
p. 2107 - 2112
(2018/04/19)
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- Synthesis of enaminones via copper-catalyzed decarboxylative coupling reaction under redox-neutral conditions
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A novel copper-catalyzed C(sp3)-H oxidative functionalization of aromatic oxime acetates with α-oxocarboxylic acids was reported. This process involved N-O/C-C bond cleavages and C-C bond formations to furnish substituted enaminones under redox-neutral conditions. The oxime acetates served as both reactants and internal oxidants. Furthermore, this transformation also features good functional group tolerance and needs no ligands or additional bases.
- Zhu, Zhongzhi,Tang, Xiaodong,Li, Jianxiao,Li, Xianwei,Wu, Wanqing,Deng, Guohua,Jiang, Huanfeng
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p. 3228 - 3231
(2017/03/20)
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- Radical Enamination of Vinyl Azides: Direct Synthesis of N-Unprotected Enamines
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An electron-withdrawing-group-generable radical-induced enamination of vinyl azides is reported, which results in a variety of β-functionalized N-unprotected enamines in a stereoselective manner. A plausible mechanism involving an unusual 1,3-H transfer of in situ generated iminyl radical intermediate was proposed on the basis of experimental results and DFT calculations.
- Ning, Yongquan,Zhao, Xue-Feng,Wu, Yan-Bo,Bi, Xihe
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supporting information
p. 6240 - 6243
(2017/11/24)
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- Oxidative Coupling of Enamines and Disulfides via Tetrabutylammonium Iodide/tert-Butyl Hydroperoxide-Mediated Intermolecular Oxidative C(sp2) S Bond Formation Under Transition Metal-Free Conditions
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The reaction of enamine compounds with disulfides in the presence of tert-butyl hydroperoxide and a catalytic amount of tetrabutylammonium iodide conveniently afforded a variety of α-thioenamine compounds through the intermolecular oxidative C(sp2) S coupling. Incorporating both of the sulfide moieties in the disulfides into the final products under oxidative conditions, this novel approach exhibits the feature of atom efficiency. A radical mechanistic pathway for the reaction process has been proposed. (Figure presented.) .
- Sun, Jiyun,Zhang-Negrerie, Daisy,Du, Yunfei
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supporting information
p. 2035 - 2040
(2016/07/16)
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- Nitrogen-Containing Analog of Dibenzoylmethanate of Boron Difluoride: Luminescence, Structure, Quantum Chemical Modeling, and Delay Fluorescence
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Boron difluoride of 3-amino-1,3-diphenyl-2-propene-1-onate (1) has been synthesized and its crystal structure has been determined. The comparative studies of 1 and its oxygen analog 1,3-diphenyl-1,3-dionate (dibenzoylmethanate) of boron difluoride (2) have been performed using the methods of stationary and time-resolved spectroscopy and quantum chemical modeling. It was established that at the transition from solutions to crystals, a bathochromic shift of the spectra and a significant increase of luminescence intensity of 1 take place. The luminescent properties of solutions of 1 and 2 are similar. The peculiarities of crystal packings of 1 and 2 are responsible for differences in crystals luminescent properties. For crystals of 2, one observes the luminescence of J-aggregates and excimers, while for 1, in which a dimer is an elementary structural fragment, only the excimer luminescence is registered. A delayed excimer fluorescence of the P-type was observed for crystals of 1 and 2 at room temperature. The intensity of the delayed fluorescence of 1 is 300-fold higher than that of 2. [Figure not available: see fulltext.]
- Fedorenko, Elena V.,Тretyakova, Galina O.,Mirochnik, Anatolii G.,Beloliptsev, Anton Yu.,Svistunova, Irina V.,Sazhnikov, Viacheslav A.,Atabekyan, Levon S.
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p. 1839 - 1847
(2016/08/25)
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- Variations in the blaise reaction: Conceptually new synthesis of 3-amino enones and 1,3-diketones
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Organic compounds with 3-amino enone or 1,3-diketone functional groups are extremely important, as they can be converted into a plethora of heterocyclic or carbocyclic compounds, or can be used as ligands in metal complexes. We have achieved a new, easy, straightforward and convenient synthesis of 3-amino enones and 1,3-diketones starting from aryl/heteroaryl/alkyl nitriles and 1-aryl/alkyl 2-bromoethanones. The reaction is a variation of the classical Blaise reaction, and it works with zinc and trimethylsilyl chloride as an activator. By running the hydrolysis of the reaction intermediate with HCl (3 N aq.) at 0-30 °C or at 100 °C, it is possible to form either 3-amino enones or 1,3-diketones, respectively. The newly developed method was used for the synthesis of avobenzone, an ingredient of sun-screen lotions. Furthermore, an easy synthesis of (Z)-3-amino-1-[4-(tertbutyl) phenyl]-3-(4-methoxyphenyl)prop-2-en-1-one, with UV/Vis absorption characteristics similar to those of avobenzone, was also achieved.
- Rao, H. Surya Prakash,Muthanna, Nandurka
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supporting information
p. 1525 - 1532
(2015/03/04)
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- Syntheses of quinazolinones from 2-iodobenzamides and enaminones via copper-catalyzed domino reactions
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N-Substituted 2-iodobenzamides and enaminones undergo cascade transformations to achieve quinazolinones via a copper-catalyzed Ullmann-type coupling, a Michael addition and a retro-Mannich reaction. A unique stereochemical feature of this domino process was that Z-enaminones reacted without external ligands, whereas E-enaminones required the assistance of ligands. This journal is
- Songsichan, Teerawat,Promsuk, Jaturong,Rukachaisirikul, Vatcharin,Kaeobamrung, Juthanat
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supporting information
p. 4571 - 4575
(2014/06/24)
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- Direct oxidative coupling of enamines and electron-deficient amines: TBAI/TBHP-mediated synthesis of substituted diaminoalkenes under metal-free conditions
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A metal-free cross-coupling of enamines and electron-de fi cient amines through oxidative C(sp2)-N bond formation has been realized by using TBAI as catalyst and TBHP as oxidant. This novel strategy allows for an efficient organocatalytic synthesis of the synthetically useful diaminoalkene derivatives and is highlighted by appealing features such as readily available of the starting materials, wide substrate scope and transition-metal-free characteristics. (Chemical Equation Presented).
- Yuan, Yucheng,Hou, Wenjuan,Zhang-Negrerie, Daisy,Zhao, Kang,Du, Yunfei
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supporting information
p. 5410 - 5413
(2015/01/09)
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- Reactions of β-diketone compounds with nitriles catalyzed by Lewis acids: A simple approach to β-enaminone synthesis
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Aluminium chloride selectively promoted the nucleophilic attack of β-diketone compounds with nitriles to give enaminones. Moreover a plausible mechanism for this transformation was given.
- Cheng, Xu,Pei, Shuchen,Xue, Chenchen,Cao, Kaifei,Hai, Li,Wu, Yong
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p. 63897 - 63900
(2015/02/19)
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- Formation of functionalized 2H-azirines through phio-mediated trifluoroethoxylation and azirination of enamines
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A variety of enaminones and enamine carboxylic esters were converted to trifluoroethoxylated 2H-azirines through reactions with PhIO in trifluoroethanol (TFE). The cascade reaction is postulated to proceed via a PhIO-mediated oxidative trifluoroethoxylation and a subsequent azirination of the α-trifluoroethoxylated enamine intermediates.
- Sun, Xiaoqian,Lyu, Youran,Zhang-Negrerie, Daisy,Du, Yunfei,Zhao, Kang
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supporting information
p. 6222 - 6225
(2014/01/17)
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- Trimethylsilyl trifluoromethanesulfonate-promoted cyclocondensation of β-ketoenamides and subsequent nonaflation to pyrid-2-yl and pyrid-4-yl nonaflates as flexible precursors for polysubstituted pyridines
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The intramolecular condensation of β-ketoenamides to 2- and/or 4-pyridone derivatives using either KOt-Bu or trimethylsilyl trifluoromethanesulfonate/Hu?nig's base was investigated. Subsequent nonaflation of the cyclization products allowed a facile purification and further functionalization through Suzuki-Miyaura couplings leading to new highly substituted pyridine derivatives. The dependence of the regioselectivity of cyclocondensation on the structure of the β-ketoenamides is discussed. Georg Thieme Verlag Stuttgart New York.
- Hommes, Paul,Berlin, Sarah,Reissig, Hans-Ulrich
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p. 3288 - 3294
(2013/12/04)
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- Copper on iron promoted one-pot synthesis of β-aminoenones and 3,5-disubstituted pyrazoles
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The reaction of hydroximoyl chlorides with acetylenes in the presence of a copper on iron bimetallic system leads to β-aminoenones via reductive ring opening of isoxazole intermediates. The valuable β-aminoenone building blocks can be isolated or transformed into pyrazoles with the addition of hydrazine in a straightforward one-pot procedure.
- Kovács, Szabolcs,Novák, Zoltán
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p. 8987 - 8993
(2013/09/24)
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- Copper-catalyzed aldol-type addition of ketones to aromatic nitriles: A simple approach to enaminone synthesis
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An efficient method for the synthesis of enaminones is described. The aldol-type addition of ketones to aromatic nitriles proceeded smoothly in the presence of a simple copper catalyst system (CuI-2,2′-bipyridine-NaO tBu) in N,N-dimethylformamide. Enaminones in satisfactory to excellent yields were produced using this technique. The Royal Society of Chemistry 2013.
- Yu, Xiaoqiang,Wang, Longxiang,Feng, Xiujuan,Bao, Ming,Yamamoto, Yoshinori
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supporting information
p. 2885 - 2887
(2013/04/24)
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- InCl3 catalysed one-pot synthesis of substituted pyrroles and 2-pyrones
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An efficient InCl3 catalysed one-pot strategy has been developed for the synthesis of tetra-substituted pyrroles and tri-substituted 2-pyrones in very good yields. Tetra-substituted pyrroles were prepared from 1,4-enediones and β-dicarbonyls employing NH4
- Mahato, Sanjit K.,Vinayagam, Jayaraman,Dey, Sumit,Timiri, Ajay K.,Chatterjee, Sourav,Jaisankar, Parasuraman
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p. 241 - 251
(2013/04/23)
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- Asymmetric synthesis of 4H-1,3-oxazines: Enantioselective reductive cyclization of N-acylated β-amino enones with trichlorosilane catalyzed by chiral Lewis bases
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N-Acylated β-amino enones reductively cyclize by treatment with trichlorosilane and a chiral Lewis base catalyst to afford optically active 4H-1,3-oxazines, which can be transformed to other chiral compounds without racemization.
- Sugiura, Masaharu,Kumahara, Mako,Nakajima, Makoto
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supporting information; experimental part
p. 3585 - 3587
(2009/12/03)
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- Solid-state synthesis of β-enamino ketones from solid 1,3-dicarbonyl compounds and ammonium salts or amines
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A facile amination of solid 1,3-dicarbonyl compounds with ammonium salts or amines in solid state has been achieved by mechanochemical grinding in the presence of KHSO4 and SiO2. Most of the reactions proceed smoothly at room temperature under solid-state conditions and give their corresponding β-imino derivatives in high yields. The method has the advantage of simple manipulation and mild conditions. Georg Thieme Verlag Stuttgart.
- Xu, Shi-Liang,Li, Cheng-Ping,Li, Jing-Hua
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experimental part
p. 818 - 822
(2009/07/18)
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- A direct oxidative route for the synthesis of pyrimidines using heteropolyacids
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Pyrimidines are synthesized via a direct oxidative one-pot, three-component, reaction between 1,3-diketone, benzaldehydes, and ammonium acetate in the presence of catalytic amounts of Keggin-type heteropolyacids under refluxing conditions in good yields.
- Heravi, Majid M.,Sadjadi, Samaheh,Oskooie, Hossein A.,Shoar, Rahim Hekmat,Bamoharram, Fatemeh F.
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body text
p. 662 - 666
(2011/03/21)
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- Photoinduced C-N bond cleavage in 2-azido-1,3-diphenyl-propan-1-one derivatives: Photorelease of hydrazoic acid
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(Chemical Equation Presented) Photolysis of 3-azido-1,3-diphenyl-propan-1- one (1a) in toluene yields 1,3-diphenyl-propen-1-one (2), whereas irradiation of 3-azido-2,2-dimethyl-1,3-diphenyl-propan-1-one (1b) results in the formation of mainly 2,2-dimethyl-1,3-diphenyl-propan-1-one. Laser flash photolysis (308 nm) of 1a,b in acetonitrile reveals a transient absorption (λmax = ~310 nm) due to the formation of radicals 4a and 4b, respectively, which have lifetimes of ~14 μs at ambient temperature. TD-DFT calculations (B3LYP/6-31+G(d)) reveal that the first and second excited states of the triplet ketone (T1K (n,π*) and T2K (π,π*)) in azide 1a are almost degenerate, at ~74 and 76 kcal/mol above the ground state (S0), respectively. Similarly, azide 1b has T1K and T2K 75 and 82 kcal/mol above S0, respectively. The calculated transition state for cleaving the C-N bond is located 71 and 74 kcal/mol above S0 in azides 1a and 1b, respectively. The calculated bond dissociation energies for breaking the C-N bond are 55 and 58 kcal/mol for azides 1a and 1b, respectively, making C-N bond breakage accessible from T 1K in azides 1 at ambient temperature. In comparison, the irradiation of azides 1 in argon matrices at 14 K lead to the formation of the corresponding triplet alkyl nitrenes (1-n), via intramolecular energy transfer from T2K- The characterization of 1-n was supported by isotope labeling, IR spectroscopy, and molecular modeling.
- Klima, Rodney F.,Jadhav, Abhijit V.,Singh, Pradeep N. D.,Chang, Mingxin,Vanos, Christine,Sankaranarayanan, Jagadis,Vu, Mai,Ibrahim, Nazarin,Ross, Elaine,McCloskey, Shaun,Murthy, Rajesh S.,Krause, Jeanette A.,Ault, Bruce S.,Gudmundsdottir, Anna D.
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p. 6372 - 6381
(2008/02/11)
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- Straightforward transformation of isoxazoles into pyrazoles: renewed and improved
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Isoxazoles bearing alkyl or carbamoyl groups were transformed into the corresponding pyrazoles in high yields by the treatment with hydrazine in methanol in the presence of a hydrogenation catalyst, e.g., Raney nickel, at ambient temperature. For the synthesis of N-substituted pyrazoles, hydrogenolysis of isoxazole followed by the treatment with substituted hydrazine was required. 3(5)-Aryl- or acylamido-substituted isoxazoles are less suitable for such transformations.
- Sviridov, Sergey I.,Vasil'ev, Andrei A.,Shorshnev, Sergey V.
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p. 12195 - 12201
(2008/02/11)
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- Reactions of 1,3-diaryl-2-chloropropane-1,3-diones with nucleophiles - Cyanide-induced retro-Claisen-Claisen condensation
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Treatment of some 1,3-diaryl-2-chloropropane-1,3-diones, acyclic chloro-substituted enaminones and β-oxo esters with nucleophiles was shown to proceed easily with the formation, at least in the first stage, of formal nucleophilic substitution products. Treatment of enaminones and β-oxo esters with azide and cyanide ions proceeds with the preservation of the skeleton, whereas chloro-substituted diaroylmethanes undergo retro-Claisen-Claisen condensation reactions in the course of the reaction with cyanide. Dibenzoylchloromethane reacts with azide and cyanide ions with fragmentation of the molecule and subsequent reassembly, resulting in benzoylated benzaldehyde cyanohydrin and a 1,3-oxathiol derivative, respectively. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
- Roshchupkina, Galina I.,Gatilov, Yury V.,Rybalova, Tatyana V.,Reznikov, Vladimir A.
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p. 1765 - 1773
(2007/10/03)
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- A novel two-step preparation of enaminoketones by amination of α,β- unsaturated ketones with methoxyamine
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β-Methoxyaminoketones, derived from the addition of methoxyamine to 1,3-diaryl-2-propen-1-one, underwent base-induced β-elimination to furnish the corresponding enaminoketones in good to moderate yields. The reaction conditions and substituents on the substrates significantly influenced the selectivity in the production of enaminoketone and/or aziridineketone.
- Seko, Shinzo,Tani, Nobuhiro
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p. 8117 - 8120
(2007/10/03)
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- Iron dichloride induced isomerization or reductive cleavage of isoxazoles: A facile synthesis of 2-carboxy-azirines
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5-Alkoxy-isoxazoles and N,N-disubstituted-5-isoxazolamines were found to isomerize to azirine derivatives by the use of iron dichloride as catalyst. On the contrary 5-alkyl- and 5-aryl-isoxazoles in the presence of the same salt, undergo reductive cleavage to enaminoketones. A common reaction intermediate is proposed.
- Auricchio, Sergio,Bini, Antonella,Pastormerlo, Eros,Truscello, Ada M.
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p. 10911 - 10920
(2007/10/03)
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- Metal-carbonyl-Induced Reaction of Isoxazoles. Ring Cleavage and Reduction by Hexacarbonylmolybdenum, Pentacarbonyliron, or Nonacarbonyldi-iron
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In the presence of and water the isoxazoles (1a-f) undergo thermally induced reductive cleavage of the N-O bond to give β-amino enones in good yield.Similar results were obtained by the use of and water with photoirradiation, or of and water with heating.A mechanism involving an N-complexed isoxazolepentacarbonylmolybdenum or isoxazoletetracarbonyliron, and a - or -complexed (β-oxo vinyl)nitrene intermediate is proposed for the reactions.The complexed nitrene moiety could be reduced by the central metal in the presence of water to give amine.Furthermore, treatment of 2-benzoyl- 3-phenyl-2-H-azirine (8a), which is an isomer of 3,5-diphenylisoxazole, with the metal carbonyls and water also resulted in the formation of a β-amino enone possibly via the corresponding complexed (β-oxo vinyl)nitrene.An N-complexed isoxazole-pentacarbonylmolybdenum intermediate was prepared by the photoreaction of with 3,5-dimethylisoxazole.Its characterization, and chemical transformations, have been carried out to investigate the proposed mechanism.
- Nitta, Makoto,Kobayashi, Tomoshige
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p. 1401 - 1406
(2007/10/02)
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- Reductive Ring Opening of Isoxazoles with Mo(CO)6 and Water
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Reaction of isoxazoles in the presence of Mo(CO)6 and water causes reductive cleavage of the N-O bond to give β-aminoenones in good yields.
- Nitta, Makoto,Kobayashi, Tomoshige
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p. 877 - 878
(2007/10/02)
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- CONVERSION OF ISOXAZOLE DERIVATIVES INTO β-AMINOENONES BY PENTACARBONYLIRON, WATER AND PHOTOIRRADIATION
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3,5-Disubstituted isoxazole derivatives, when irradiated in the presence of pentacarbonyliron and water undergo reductive cleavage of the N-O bond to give β-aminoenones in good yields.
- Nitta, Makoto,Kobayashi, Tomoshige
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p. 3925 - 3928
(2007/10/02)
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