- Iridium-catalyzed highly chemoselective and efficient reduction of nitroalkenes to nitroalkanes in water
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An iridium-catalyzed highly chemoselective and efficient transfer hydrogenation reduction of structurally diverse nitroalkenes was realized at very low catalyst loading (S/C = up to 10000 or 20?000), using formic acid or sodium formate as a traceless hydride donor in water. Excellent functionality tolerance is also observed. The turnover number and turnover frequency of the catalyst reach as high as 18?600 and 19?200 h-1, respectively. An inert atmosphere protection is not required. The reactivities of nitroalkenes are dependent on their substitution pattern, and the pH value is a key factor to accomplish the complete conversion and excellent chemoselectivity. Purification of products is achieved by simple extraction without column chromatography. The reduction procedure is facilely amplified to 10 g scale at 10?000 S/C ratio. The potential of this green reduction in enantioselective hydrogenation has been demonstrated.
- Chen, Yang,Liu, Changmeng,Xu, Dong,Xu, Jiaxi,Yang, Zhanhui
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supporting information
p. 6050 - 6058
(2021/08/23)
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- Organocatalytic enantioselective formal C(sp2)-H alkylation
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An organocatalytic enantioselective formal C(sp2)-H alkylation is reported. This alkylative desymmetrization of prochiral 2,2-disubstituted cyclopentene-1,3-dione is catalyzed by a bifunctional tertiary aminourea derivative, utilizes air-stable and inexpensive nitroalkanes as the alkylating agents, and delivers synthetically versatile five-membered carbocycles containing an all-carbon quaternary stereogenic center remote from the reaction site in excellent enantioselectivity.
- Manna, Madhu Sudan,Mukherjee, Santanu
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supporting information
p. 130 - 133
(2015/01/30)
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- Useful extensions of the henry reaction: Expeditious routes to nitroalkanes and nitroalkenes in aqueous media
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The products of the Henry nitroaldol reaction from nitromethane and several aldehydes were reduced to the corresponding nitroalkanes with (n-Bu) 3SnH in water under microwave irradiation (80 °C/10 min), or dehydrated to the corresponding nitroalkenes with K2CO3 in water (generally 0-5 °C/20 min). Both "one-pot" reactions occur in excellent yields across a range of aliphatic and aromatic (including heteroaromatic) substrates. It seems likely that the deoxygenation of the nitroaldols occurs via coordination of an oxygen atom of the nitro group with a tin atom, which facilitates hydride delivery in the transition state. The elimination of water from the nitroaldols in mild base is likely driven by the stability of the conjugated nitroalkene products. The elimination required workup with 2 N HCl, which likely displaces a nitroalkane-nitroalkene equilibrium towards the latter. These extensions of the Henry reaction lead to products not easily obtained otherwise.
- Chandrasekhar, Sosale,Shrinidhi, Annadka
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p. 3008 - 3018
(2014/10/16)
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- New approach to oximes through reduction of nitro compounds enabled by visible light photoredox catalysis
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A range of nitro compounds are smoothly reduced to their corresponding oximes under the synergistic effects of visible light irradiation, the Ru(bpy)3Cl2 photocatalyst, Hünig's base, Mg(ClO 4)2 activation, and MeCN solvent. This remarkably mild and environmentally benign protocol, when orchestrated with classical Beckmann rearrangement, enables such high-value industrial feedstock as caprolactam to be readily accessed from simple precursor nitrocyclohexane.
- Cai, Shunyou,Zhang, Shaolong,Zhao, Yaohong,Wang, David Zhigang
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p. 2660 - 2663
(2013/07/11)
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- Tuning the lewis acidity of boranes in frustrated lewis pair chemistry: Implications for the hydrogenation of electron-poor alkenes
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An analysis of the metal-free reduction of electron deficient olefins by frustrated Lewis pairs indicates that the rate-determining step might be either the heterolytic cleavage of H2 to form an -onium borohydride salt, or the subsequent transfer of the hydride moiety to the substrate following a Michael-type addition reaction. While the use of strong Lewis acids such as B(C6F5)3 facilitates the first of these processes, hydride transfer to the olefin should be contrarily favoured by the use of weak Lewis acids which, for this very same reason, might be unable to promote the prior H2 split. After systematic testing of several boranes of different Lewis acidity (assessed by using the Childs' method) and steric demand, an optimal situation that employs tris(2,4,6-trifluorophenyl) borane was reached. Mixtures of this borane with 1,4-diazabicyclo[2.2.2]octane (DABCO) exhibited excellent catalytic activity for the hydrogenation of alkylidene malonates. In fact, this transformation could be achieved under milder conditions than those we reported previously. Moreover, the reaction scope could be expanded to other electron deficient olefins containing esters, sulfones or nitro functionalities as electron-withdrawing substituents.
- Nicasio, Juan A.,Steinberg, Sebastian,Ines, Blanca,Alcarazo, Manuel
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p. 11016 - 11020
(2013/09/02)
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- Functional-group tolerance in frustrated lewis pairs: hydrogenation of nitroolefins and acrylates
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Weak Lewis acid for high nucleophilicity: Hydridoborate derived from B(2,6-F2C6H3)3 shows significant hydride character. Solid-state and solution structure analysis revealed a dihydrogen-bonded aggregate. The new frustrated Lewis pair was applied in the hydrogenation of nitroolefins and acrylates (see scheme; EWG=electron- withdrawing group). The decreased Lewis acidity provides higher reactivity and functional-group tolerance. Copyright
- Greb, Lutz,Daniliuc, Constantin-Gabriel,Bergander, Klaus,Paradies, Jan
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supporting information
p. 5876 - 5879
(2013/07/05)
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- Visible-light-promoted C-C bond cleavage: Photocatalytic generation of iminium ions and amino radicals
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Photoscissors: Structurally variable and synthetically robust iminium ions and amino radicals species could be simultaneously generated by visible-light-promoted photoredox cleavage of the C-C bonds in simple vicinal diamine precursors under very mild reaction conditions. Copyright
- Cai, Shunyou,Zhao, Xinyang,Wang, Xinbo,Liu, Qisong,Li, Zigang,Wang, David Zhigang
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p. 8050 - 8053
(2012/08/29)
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- S-benzyl isothiouronium chloride as a recoverable organocatalyst for the reduction of conjugated nitroalkenes with Hantzsch ester
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The reduction of conjugated nitroalkenes into nitroalkanes with Hantzsch ester using S-benzyl isothiouronium chloride as a recoverable organocatalyst was successfully accomplished with high yield and excellent chemoselectivity.
- Nguyen, Quynh Pham Bao,Kim, Jae Nyoung,Kim, Taek Hyeon
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supporting information; experimental part
p. 6513 - 6516
(2012/08/28)
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- Catalyst-free and solventless Hantzsch ester mediated reduction of nitroolefins at elevated temperature
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A catalyst-free and solventless protocol for the reduction of nitroolefins to the corresponding nitroalkanes at 100°C has been developed. Various nitroalkenes have been reduced in good to excellent yield with short reaction times.
- Chauhan, Pankaj,Kaur, Kirandeep,Bala, Neeraj,Kumar, Vikas,Chimni, Swapandeep Singh
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experimental part
p. 304 - 309
(2011/05/02)
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- Characterization of xenobiotic reductase A (XenA): Study of active site residues, substrate spectrum and stability
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Xenobiotic reductase A (XenA) has broad catalytic activity and reduces various α,β-unsaturated and nitro compounds with moderate to excellent stereoselectivity. Single mutants C25G and C25V are able to reduce nitrobenzene, a non-active substrate for the wild type, to produce aniline. Total turnover is dominated by chemical rather than thermal instability. The Royal Society of Chemistry 2010.
- Yanto, Yanto,Yu, Hua-Hsiang,Hall, Melanie,Bommarius, Andreas S.
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supporting information; scheme or table
p. 8809 - 8811
(2011/02/28)
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- Organocatalytic biomimetic reduction of conjugated nitroalkenes
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A thiourea-catalyzed biomimetic reduction of conjugated nitroalkenes has been developed. Various aromatic and aliphatic conjugated nitroalkenes can be reduced to give the respective nitroalkanes with good yields under mild conditions. This protocol is not only practical, but may also provide insight into the mechanisms of redox transformations in biological systems. Georg Thieme Verlag Stuttgart.
- Zhang, Zhiguo,Schreiner, Peter R.
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p. 2559 - 2564
(2008/03/13)
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- ROMPgel-supported tris(triphenylphosphine)rhodium(I) chloride: A selective hydrogenation catalyst for parallel synthesis
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ROMPgel-supported tris(triphenylphosphine)rhodium(I) chloride has been prepared and the immobilised catalyst has been effectively employed in selective hydrogenations of a variety of alkenes and terminal alkynes.
- ?rstad, Erik,Barrett, Anthony G. M.,Tedeschi, Livio
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p. 2703 - 2707
(2007/10/03)
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- Intramolecular Diels-Alder reaction of dinitro-olefin derivatives of furan for the preparation of a versatile tool: 3,7-Dinitro-11- oxatricycloundec-9-ene
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Recurrent additions of nitromethane on furfuraldehyde followed by an intramolecular DielsAlder reaction allowed the obtention of the title compound 1 in good yield with excellent stereoselectivity. Aromatization, ether cleavage and stereocontrolled oxidation reactions give evidence of the synthetic versatility of this adduct in the preparation of ergot alkaloids and valienamine bicyclic.
- Sader-Bakaouni, Lina,Charton, Olivier,Kunesch, Nicole,Tillequin, Francois
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p. 1773 - 1782
(2007/10/03)
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- Zeolite (H-ZSM 5)-catalysed reduction of conjugated nitroalkenes with sodium cyanoborohydride
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Conjugated nitroalkenes are readily reduced to the corresponding nitroalkanes with sodium cyanoborohydride in the presence of the zeolite H-ZSM 5 in methanol.
- Gupta, Anuradha,Haque, Azizul,Vankar, Yashwant D.
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p. 1653 - 1654
(2007/10/03)
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- REDUCTION OF AROMATIC NITROALKENES WITH BAKER'S YEAST
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Aromatic nitroalkenes were reduced chemoselectively with baker's yeast to give the corresponding nitroalkanes.
- Takeshita, Mitsuhiro,Yoshida, Sachiko,Kohno, Yoichiro
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p. 553 - 562
(2007/10/02)
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- SYNTHESIS AND PROPERTIES OF FURAN DERIVATIVES. 1. SYNTHESIS OF 3,5-DISUBSTITUTED Δ2-ISOXAZOLINES CONTAINING FURFURYL FRAGMENTS
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3,5-Disubstituted Δ2-isoxazolines containing furan fragments have been synthesized by 1,3-dipolar cycloaddition reactions.
- Karakhanov, R. A.,Bogacheva, E. S.,Romero, I.,Kelarev, V. I.
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p. 354 - 357
(2007/10/02)
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- SYNTHESIS OF 2,3-DIHYDRO-1H-PHENALENE DERIVATIVE BY THE INTRAMOLECULAR DIELS-ALDER REACTION OF BENZYNE WITH FURAN
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2,3-Dihydro-1H-phenalene derivative 1 was synthesized by the intramolecular Diels-Alder reaction (21->22). 2,5-Dimethylpyrrole was used as a protecting group for the primary amine.
- Darlington, W. H.,Szmuszkovicz, J.
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p. 1883 - 1886
(2007/10/02)
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- A Highly Chemoselective Reduction of Conjugated Nitro Olefins with Hantzsch Ester in the Presence of Silica Gel
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An effective system to reduce conjugated nitro olefins into the corresponding nitroalkanes is described.The system composed Hantzsch ester (HEH) and silica gel in benzene exerts high yield and excellent chemoselectivity under almost neutral conditions.Facile applications of the system to the syntheses of natural products are also described.
- FUJI, Masayuki
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p. 4029 - 4036
(2007/10/02)
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- In Situ Generation and Synthetic Application of 2-Phenylbenzimidazoline to the Selective Reduction of Carbon-Carbon Double Bonds of Electron-Deficient Olefins
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2-Phenylbenzimidazoline (PBI) as a mild, selective, and convenient reducing agent was efficiently generated in situ from o-phenylenediamine and benzaldehyde in alcohols.A generally applicable method for the selective reduction of carbon-carbon double bonds of a variety of electron-deficient olefins with an alcoholic solution of PBI is described.The reduction of α,β-unsaturated ketones to the corresponding saturated ketones could also be accomplished (but, less effectively) with PBI with the aid of a Lewis-acid catalyst. 1-Methyl-2-(o-nitrophenyl)benzimidazoline prepared and isolated by the reaction of o-nitrobenzaldehyde with N-methyl-o-phenylenediamine reduced benzylidenemalononitrile to give benzylmalononitrile and 1-methyl-2-(o-nitrophenyl)benzimidazoline in high yields.This shows the validity of PBI to be the actual reducing species in the present reduction system.From a mechanistic study, the present reductions could be interpreted in terms of a mechanism involving a synchronous transport of a pair of hydrogens or a sequential transfer of a hydride and a proton from PBI to the olefins.
- Chikashita, Hidenori,Nishida, Shuichi,Miyazaki, Makoto,Morita, Yasuhiro,Itoh, Kazuyoshi
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p. 737 - 746
(2007/10/02)
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- REDUCTION OF NITRO ALKENES BY A MODEL OF NAD(P)H
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Carbon-carbon double bonds in α,β-unsaturated nitro compounds are reduced smoothly into the corresponding nitro alkanes by a model of NAD(P)H in benzene in the presence of silica gel.Other functional groups are inert under the reaction conditions.
- Nakamura, Kaoru,Fujii, Masayuki,Oka, Shinzaburo,Ohno, Atsuyoshi
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p. 523 - 526
(2007/10/02)
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- Nitroethylene: A Stable, Clean, and Reactive Agent for Organic Synthesis
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Contrary to current belief, nitroethylene is a stable reagent and holds promise as a useful and reactive synthon.Nitroethylene can be prepared in 20-25-g lots, and standard, refrigerated solutions in common solvents provide a good and ready source of the reagent.The reagent purity can be easily monitored by titration against tetraphenylcyclopentadienone (tetracyclone) coupled with the isolation of the colorless crystalline adduct.With reactive substrates, nitroethylene reacts with greatest ease at low temperatures, leading to functionalized systems having potential for further elaboration.With systems that require heating, the limited stability of nitroethylene itself complicates the course of the reaction.Cyclopentadiene, 5-cyclopentadiene, 5-(methoxymethyl)cyclopentadiene, 5-(1,3-dithianyl)cyclopentadiene, 5-(trimethylsilyl)cyclopentadiene, and spiroheptadiene readily gave (4 + 2) adducts with nitroethylene, each possessing attraction as a synthetic intermediate.Adducts from furan and acetoxyfulvene undergo rearrangement via ? cleavage.The (4 + 2) adduct from 9-diazofluorene spontaneously extrudes nitrogen, leading to spironitrocyclopropane.Indole readily undergoes Michael addition to give 80percent 3-(nitroethyl)indole and 15percent of novel bis adduct.The 2,6 Michael adduct arises with 1-morpholinocyclohexene, and β-pinene undegoes an ene reaction with nitroethylene.Novel 2-nitroethyl phosphonates, useful in Wittig-Horner reactions, arise from nitroethylene and phosphites in tert-butyl alcohol.
- Ranganathan, Darshan,Rao, C.Bhushan,Ranganathan, Subramania,Mehrotra, Ashok K.,Iyengar, Radha
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p. 1185 - 1189
(2007/10/02)
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