- Rh(I)-catalyzed solvent-free ortho-alkylation of aromatic imines under microwave irradiation
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The synthesis of ortho-alkylated ketones through a chelation-assisted Rh (I) catalyzed ortho-alkylation reaction of aromatic imines under microwave activated solvent-free conditions in monomode reactors was performed. These conditions have been also applied to hydroacylation and ortho-alkylation reactions with aldimines.
- Vo-Thanh, Giang,Lahrache, Hind,Loupy, André,Kim, In-Jung,Chang, Duck-Ho,Jun, Chul-Ho
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Read Online
- Redox-Neutral Imination of Alcohol with Azide: A Sustainable Alternative to the Staudinger/Aza-Wittig Reaction
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The traditional Staudinger/aza-Wittig reaction represents one of the most powerful tools for imine formation. However, for this multistep procedure, the sacrificial phosphine has to be used, resulting in difficulties in the purification process and waste disposal at the same time. Here, we report a redox-neutral azide-alcohol imination methodology enabled by a base-metal nickel PN3 pincer catalyst. The one-step, waste-free, and high atom-economical features highlight its advantages further. Moreover, mechanistic insight suggests a non-metal-ligand cooperation pathway based on the observation of an intermediate and density functional theory calculations.
- Li, Huaifeng,Lupp, Daniel,Das, Pradip K.,Yang, Li,Gon?alves, Théo P.,Huang, Mei-Hui,El Hajoui, Marwa,Liang, Lan-Chang,Huang, Kuo-Wei
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p. 4071 - 4076
(2021/04/12)
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- Base-Catalyzed [3 + 2] Cycloaddition of N-Benzyl Ketimines to Arylacetylenes Followed by Oxidation: A One-Pot Access to Polyarylated 2 H-Pyrroles via Intermediate Pyrrolines
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N-Benzyl ketimines undergo [3 + 2] cycloaddition with arylacetylenes in the KOBut/DMSO solution to 2,3,5-triarylpyrrolines, which are oxidized (chloranil, DDQ) in situ to 2,3,5-triaryl-2H-pyrroles in 53-71% yields. The intermediate 1-pyrrolines can be isolated in 31-91% yields and separately oxidized to the corresponding 2H-pyrroles.
- Bidusenko, Ivan A.,Schmidt, Elena Yu.,Trofimov, Boris A.,Ushakov, Igor A.,Vashchenko, Alexander V.
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supporting information
p. 4121 - 4126
(2021/06/28)
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- Enantioselective reduction of: N -alkyl ketimines with frustrated Lewis pair catalysis using chiral borenium ions
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Enantioselective reduction of ketimines was demonstrated using chiral N-heterocyclic carbene (NHC)-stabilised borenium ions in frustrated Lewis pair catalysis. High levels of enantioselectivity were achieved for substrates featuring secondary N-alkyl substituents. Comparative reactivity and mechanistic studies identify key determinants required to achieve useful enantioselectivity and represent a step forward in the further development of enantioselective FLP methodologies.
- Mercea, Dan M.,Howlett, Michael G.,Piascik, Adam D.,Scott, Daniel J.,Steven, Alan,Ashley, Andrew E.,Fuchter, Matthew J.
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supporting information
p. 7077 - 7080
(2019/06/20)
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- Merrifield resin-supported quinone as an efficient biomimetic catalyst for metal-free, base-free, chemoselective synthesis of 2,4,6-trisubstituted pyridines
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Metal-free, base-free, biomimetic and chemoselective synthesis of 2,4,6-trisubstituted pyridines was developed under mild conditions for the first time. The heterogeneous biomimetic catalyst-recoverable Merrifield resin-supported quinone-was fully characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectrometry (XPS) and energy dispersive X-ray spectroscopy (EDX). This supported quinone catalyst exhibited excellent catalytic reactivity for chemoselective synthesis of 2,4,6-trisubstituted pyridines, providing an efficient and green method for the synthesis of pyridine derivatives under mild conditions. Mechanistic investigations were conducted to gain insights into the heterogeneous biomimetic catalyst as well as the resulting transformation. The successful capture of intermediates offered direct and clear evidence for the proposed mechanism.
- Yang, Qing,Zhang, Yilin,Zeng, Wei,Duan, Zheng-Chao,Sang, Xinxin,Wang, Dawei
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p. 5683 - 5690
(2019/10/22)
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- Au nanoparticle-immobilized L-cysteine-paired porous ionic copolymer as an efficient catalyst for additive-free oxidative coupling of alcohols and amines
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Herein, an L-cysteine-paired ionic copolymer (DVB-[MimLcy]n) with mesoporosity was prepared by free radical copolymerization of divinylbenzene (DVB) and imidazolium ionic liquids (ILs), followed by anion-exchange with L-cysteine. Because of the rich functional groups of –NH2, –SH, and –COO– and the porous framework, the DVB-[MimLcy]3 was revealed to be an ideal stabilizer for metal nanoparticles (NPs). Highly uniform dispersed small Au NPs (2–3 nm) immobilized on DVB-[MimLcy]3 (Aua/DVB-[MimLcy]3) can act as an efficient heterogeneous catalyst for additive-free synthesis of imines through coupling of a broad range of alcohols and organic amines and can be easily recovered and steadily reused several times.
- Du, Shengyu,Zhang, Chenjun,Jiang, Yuchen,Jiang, Pingping,Leng, Yan
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- New synthetic access to 3-fluoroalkyl-5-pyrazolecarboxylates and carboxylic acids
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A novel process for preparing 3-fluoroalkyl-5-pyrazolecarboxylates and carboxylic acids is hereby presented. Easily accesible α-fluorinated ketimines were condensed with oxalyl monochloride derivatives, and the obtained vinamides underwent acid-catalyzed cyclization with substituted hydrazines. This highly efficient protocol can also be used for non-fluorinated C-3 and C-5 substituents.
- Herrera, Alberto Gómez,Schmitt, Etienne,Panossian, Armen,Vors, Jean-Pierre,Pazenok, Sergii,Leroux, Frédéric R.
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- Efficient Synthesis of Amines by Iron-Catalyzed C=N Transfer Hydrogenation and C=O Reductive Amination
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Here we report the catalytic transfer hydrogenation (CTH) of non-activated imines promoted by a Fe-catalyst in the absence of Lewis acid co-catalysts. Use of the (cyclopentadienone)iron complex 1, which is much more active than the classical ‘Kn?lker complex’ 2, allowed to reduce a number of N-aryl and N-alkyl imines in very good yields using iPrOH as hydrogen source. The reaction proceeds with relatively low catalyst loading (0.5–2 mol%) and, remarkably, its scope includes also ketimines, whose reduction with a Fe-complex as the only catalyst has little precedents. Based on this methodology, we developed a one-pot CTH protocol for the reductive amination of aldehydes/ketones, which provides access to secondary amines in high yield without the need to isolate imine intermediates. (Figure presented.).
- Facchini, Sofia Vailati,Cettolin, Mattia,Bai, Xishan,Casamassima, Giuseppe,Pignataro, Luca,Gennari, Cesare,Piarulli, Umberto
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supporting information
p. 1054 - 1059
(2018/01/27)
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- Asymmetric transfer hydrogenation reactions of: N -sulfonylimines by using alcohols as hydrogen sources
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A palladium/zinc co-catalytic system was established and successfully utilized in the asymmetric transfer hydrogenation reactions of N-sulfonylimines with alcohols as hydrogen sources. Simple alcohols such as methanol, ethanol and benzyl alcohols are all
- Yang, Fan,Chen, Jingchao,Shen, Guoli,Zhang, Xuexin,Fan, Baomin
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supporting information
p. 4963 - 4966
(2018/05/23)
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- Acid-catalyzed tandem reaction for the synthesis of pyridine derivatives via C=C/C(sp3)-N bond cleavage of enones and primary amines
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A one-pot acid-catalyzed tandem reaction has been developed without any metallic reagents or extra oxidants. This reaction involves a C=C bond cleavage of enones via a “masked” reverse Aldol reaction, and C(sp3)-N bond cleavage of primary amines to provide nitrogen sources for the assembly of pyridine derivatives in high yields with excellent functional group tolerance.
- Mao, Zhong-Yuan,Liao, Xiao-Yun,Wang, Heng-Shan,Wang, Chun-Gu,Huang, Ke-Bin,Pan, Ying-Ming
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p. 13123 - 13129
(2017/03/11)
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- Aerobic oxidative coupling of alcohols and amines towards imine formation by a dicopper(I,I) catalyst
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A dicopper(I,I) complex [Cu2(L1) (Cl)2] (1), bearing a Cu2Cl2 core spanned by a naphthyridine–diimine ligand is synthesized by the treatment of CuCl with 2,7–bis(N–mesitylmethylimino)–1,8–naphthyridine (L1). The catalytic efficacy of 1 is assessed for aerobic oxidative synthesis of imines from alcohols and amines. The title complex is found to be an excellent catalyst for a wide variety of alcohols and amines. Kinetic experiments revealed the involvement of both copper ions in the aerobic oxidation process. The general utility of naphthyridine based ligands to favour a possible bimetallic pathway for a catalytic reaction is demonstrated here.
- Dutta, Indranil,De, Subhabrata,Yadav, Sudhir,Mondol, Ranajit,Bera, Jitendra K.
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p. 117 - 124
(2017/09/30)
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- P-N Cooperative Borane Activation and Catalytic Hydroboration by a Distorted Phosphorous Triamide Platform
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Studies of the stoichiometric and catalytic reactivity of a geometrically constrained phosphorous triamide 1 with pinacolborane (HBpin) are reported. The addition of HBpin to phosphorous triamide 1 results in cleavage of the B-H bond of pinacolborane through addition across the electrophilic phosphorus and nucleophilic N-methylanilide sites in a cooperative fashion. The kinetics of this process of were investigated by NMR spectroscopy, with the determined overall second-order empirical rate law given by ν = -k[1][HBpin], where k = 4.76 × 10-5 M-1 s-1 at 25 °C. The B-H bond activation process produces P-hydrido-1,3,2-diazaphospholene intermediate 2, which exhibits hydridic reactivity capable of reacting with imines to give phosphorous triamide intermediates, as confirmed by independent synthesis. These phosphorous triamide intermediates are typically short lived, evolving with elimination of the N-borylamine product of imine hydroboration with regeneration of the deformed phosphorous triamide 1. The kinetics of this latter process are shown to be first-order, indicative of a unimolecular mechanism. Consequently, catalytic hydroboration of a variety of imine substrates can be realized with 1 as the catalyst and HBpin as the terminal reagent. A mechanistic proposal implicating a P-N cooperative mechanism for catalysis that incorporates the various independently verified stoichiometric steps is presented, and a comparison to related phosphorus-based systems is offered.
- Lin, Yi-Chun,Hatzakis, Emmanuel,McCarthy, Sean M.,Reichl, Kyle D.,Lai, Ting-Yi,Yennawar, Hemant P.,Radosevich, Alexander T.
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supporting information
p. 6008 - 6016
(2017/05/04)
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- Hydroboration Catalyzed by 1,2,4,3-Triazaphospholenes
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The synthesis and study of the catalytic activity of 1,2,4,3-triazaphospholenes (TAPs) is reported. TAPs represent a more modular scaffold than previously reported diazaphospholenes. TAP halides were shown to catalyze the 1,2 hydroboration of 19 imines, and three α,β unsaturated aldehydes with pinacolborane, including examples that did not undergo hydroboration by previously reported diazaphospholene systems. DFT calculations support a mechanism where a triazaphospholene cation interacts with the substrate, a mechanism distinct from diazaphospholene catalyzed hydroborations.
- Tien, Chieh-Hung,Adams, Matt R.,Ferguson, Michael J.,Johnson, Erin R.,Speed, Alexander W. H.
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supporting information
p. 5565 - 5568
(2017/10/25)
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- Synthesis of 4-Isoxazolines via Visible-Light Photoredox-Catalyzed [3 + 2] Cycloaddition of Oxaziridines with Alkynes
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A method for [3 + 2] cycloaddition of oxaziridines with alkynes to form 4-isoxazolines via visible-light photoredox catalysis is described. This method is a greener, atom-economical reaction that tolerates various functional groups and provides good to excellent yield. Moreover, the cyclization products can be conveniently converted into tetrasubstituted allylic alcohols and enamines. A mechanistic study suggests that the reaction involves photoredox-catalyzed in situ generation of a nitrone from the oxaziridine by SET.
- Jang, Gwang Seok,Lee, Junggeun,Seo, Jungseok,Woo, Sang Kook
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supporting information
p. 6448 - 6451
(2017/12/08)
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- Iridium(I) Complexes Bearing a Noninnocent PNP-Pincer-Type Phosphaalkene Ligand: Catalytic Application in the Base-Free N-Alkylation of Amines with Alcohols
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A series of IrI complexes [Ir(L)(PPEP?)] [L = Cl- (3), CO (4), tBuNC (5), PMe3 (6), PPh3 (7)], coordinated with a PNP-pincer-type phosphaalkene ligand bearing a dearomatized pyridine ring (PPEP?), have been prepared and their catalytic properties for the dehydration/condensation of amines with alcohols has been examined. The catalytic reactions successfully proceed under base-free conditions to give N-alkylated amines and their dehydrogenation derivatives (imines). The product selectivity is dependent on L coordinated with Ir(PPEP?). Complexes 4 and 5 that contain π-accepting ligands (CO, tBuNC) form N-alkylated amines as the major products in a closed system using a nitrogen-gas-filled Schlenk tube. In contrast, complex 7 that contain PPh3 as L produces imines as the major products under a nitrogen-gas flow. The reason for the selectivity change depending on L is discussed based on stoichiometric reactions using model compounds of presumed catalytic intermediates. PNP-pincer-type phosphaalkene complexes of IrI bearing a dearomatized pyridine ring have been found to catalyze the dehydration/condensation of amines with alcohols under base-free conditions to afford N-alkylated amines and imines in high yields. The product selectivity can be controlled by the choice of auxiliary ligands (L) as well as the reaction conditions.
- Chang, Yung-Hung,Tanigawa, Ippei,Taguchi, Hiro-Omi,Takeuchi, Katsuhiko,Ozawa, Fumiyuki
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p. 754 - 760
(2016/03/01)
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- Metal-free oxidative cross-coupling of diazirines with arylboronic acids
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We report herein a metal-free cross-coupling of diazirines with arylboronic acids under oxidative conditions. The reaction affords a series of substituted olefins. It is proposed that the interaction between the nitrogen on diazirine with arylboronic acid plays a key role in this transformation.
- Wu, Guojiao,Zhao, Xia,Ji, Wenzhi,Zhang, Yan,Wang, Jianbo
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supporting information
p. 1961 - 1963
(2016/02/05)
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- Synthesis and catalytic reactivity of bis(amino)cyclopropenylidene carbene-borane adducts
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The first reported neutral boron(III) adducts of bis(amino)cyclopropenylidene carbenes (BAC carbenes) have been synthesized, structurally characterized, and applied in homogeneous reaction chemistry. These air-stable adducts have been prepared by the combination of a BAC carbene lithium tetrafluoroborate adduct with borane dimethyl sulfide, boron trifluoride etherate, or dicyclohexylborane. A borenium cation derived in situ from the dicyclohexylborane adduct catalytically reduces unhindered benzyl ketimines, a class of substrate that cannot be reduced by prior borenium catalysts, at room temperature, employing 20 atm of hydrogen gas as the terminal reductant.
- Huchenski, Blake S. N.,Adams, Matt R.,McDonald, Robert,Ferguson, Michael J.,Speed, Alexander W. H.
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supporting information
p. 3101 - 3104
(2016/10/09)
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- First efficient two-step/one-pot zirconium (IV)isopropoxide-mediated reductive amination of carbonyl compounds
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An efficient method for the synthesis of various primary and secondary amines through a zirconium(IV) isopropoxide-mediated reductive amination reaction of aldehydes and ketones is reported. A series of different aldehydes, ketones and amines were used leading to the expected amino products in moderate to excellent yields. The mechanistic rationale of this reaction has been postulated through the formation of a transient imine species and a diastereoselective version using (R)-phenylethylamine as chiral inducer led to the expected products in moderate to excellent yields and with diastereoselectivities up to 100%.
- Pieri, Cyril,Brunel, Jean Michel
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p. 448 - 456
(2015/06/22)
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- Copper-Catalyzed Formation of α-Alkoxycycloalkenones from N-Tosylhydrazones
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The combination of 20 mol % of copper iodide and lithium tert-butoxide triggers the formation of a broad range of substituted, functionalized α-alkoxy 2H-naphthalenones from readily available N-tosylhydrazones. The data suggests that this transformation occurs through cycloaddition of a copper carbenoid with an ester, followed by a Lewis acid-catalyzed [1,2] alkyl shift of the in situ generated alkoxyepoxide intermediate. The combination of 20 mol % of copper iodide and lithium tert-butoxide triggers the formation of a broad range of substituted, functionalized α-alkoxy 2H-naphthalenones from readily available N-tosylhydrazones. The reaction proceeds by the cycloaddition of a copper carbenoid with an ester, and a subsequent Lewis acid-catalyzed [1,2] alkyl shift of the in situ generated alkoxyepoxide intermediate.
- Su, Naijing,Theorell, Juliana A.,Wink, Donald J.,Driver, Tom G.
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supporting information
p. 12942 - 12946
(2015/11/02)
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- Catalytic acceptorless dehydrogenations: Ru-Macho catalyzed construction of amides and imines
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A commercially available ruthenium(II) PNP type pincer catalyst (Ru-Macho) promotes formation of amides and imines from alcohols and amines via an acceptorless dehydrogenation pathway. The formation of secondary amides, tertiary amides, and secondary ketimines occurs in yields ranging from 35% to 95%.
- Oldenhuis, Nathan J.,Dong, Vy M.,Guan, Zhibin
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supporting information
p. 4213 - 4218
(2014/06/09)
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- Experimental analysis of the catalytic cycle of the borane-promoted imine reduction with hydrosilanes: Spectroscopic detection of unexpected intermediates and a refined mechanism
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The discovery of intermediates that had not been seen before in imine reduction involving borane-mediated Si-H bond activation provided new insight into the mechanism, eventually leading to a refined catalytic cycle that also bears relevance to asymmetric variants. The catalysis proceeds through an ion pair composed of a silyliminium ion and a borohydride that subsequently reacts to yield an N-silylated amine and the borane catalyst. The latter step is enantioselectivity-determining when using a chiral borane. It was now found that there are additional intermediates that profoundly influence the outcome of such enantioselective transformations. Significant amounts of the corresponding free amine and N-silylated enamine are present in equimolar ratio during the catalysis. The free amine emerges from a borohydride reduction of an iminium ion (protonated imine) that is, in turn, generated in the enamine formation step. The unexpected alternative pathway adds another enantioselectivity-determining hydride transfer to reactions employing chiral boranes. The experiments were done with an axially chiral borane that was introduced by us a few years ago, and the refined mechanistic picture helps to understand previously observed inconsistencies in the level of enantioinduction in reductions catalyzed by this borane. Our findings are general because the archetypical electron-deficient borane B(C6F5)3 shows the same reaction pattern. This must have been overlooked in the past because B(C 6F5)3 is substantially more reactive than our chiral borane with just one C6F5 group. Reactions with B(C6F5)3 must be performed at low catalyst loading to allow for detection of these fundamental intermediates by NMR spectroscopy.
- Hermeke, Julia,Mewald, Marius,Oestreich, Martin
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supporting information
p. 17537 - 17546
(2014/01/06)
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- Dissociation or cyclization: Options for a triad of radicals released from oxime carbamates
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A set of oxime carbamates having N-alkyl and N,N-dialkyl substituents were prepared via carbonyldiimidazole intermediates. It was shown by EPR spectroscopy that they underwent clean homolysis of their N-O bonds upon UV photolysis. During photolysis of acetophenone O-allylcarbamoyl oxime, the corresponding oxazolidin-2-onylmethyl radical was detected by EPR spectroscopy, providing the first evidence that N-monosubstituted carbamoyloxyl radicals can hold their structural integrity. N,N-Disubstituted carbamoyloxyl radicals dissociated rapidly at the lowest accessible temperatures. Above room temperature, both types of oxime carbamate acted as selective new precursors for aminyl and iminyl radicals. Rate parameters were measured for 5-exo cyclization of N-benzyl-N-pent-4-enylaminyl radicals; the rate constant was smaller than for C-centered and O-centered analogues. Oxime carbamates derived from the volatile diethylamine afforded aryliminyl radicals that proved convenient for phenanthridine preparations.
- McBurney, Roy T.,Walton, John C.
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supporting information
p. 7349 - 7354
(2013/06/27)
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- Practical synthesis of polysubstituted imidazoles via iodine- Catalyzed aerobic oxidative cyclization of aryl ketones and benzylamines
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A practical synthetic method for polysubstituted imidazoles via iodine-catalyzed aerobic oxidative cyclization of aryl ketones and benzylamines has been developed. It was found to tolerate a broad range of substrates to prepare polysubstituted imidazole derivatives in a one-pot manner, and thus importantly allowed product diversity for imidazole chemistry. Additionally, the resultant 1,2,4-trisubstituted imidazoles could be conveniently transformed to functionalized 1,2,4,5-tetrasubstituted imidazoles via electrophilic substitution or direct C-H functionalization, or 2,4-diaryl-1H-imidazoles by debenzylation reaction, which further indicates potential applications of this method in synthetic and pharmaceutical chemistry. Copyright
- Huang, Huawen,Ji, Xiaochen,Wu, Wanqing,Jiang, Huanfeng
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p. 170 - 180
(2013/03/13)
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- Asymmetric organocatalytic reduction of ketimines with catecholborane employing a N-triflyl phosphoramide Br?nsted acid as catalyst
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The first asymmetric reduction of ketimines with catecholborane employing an enantiopure N-triflyl phosphoramide as the organocatalyst has been developed. Five mole % of the catalyst provides the corresponding secondary amines in very good to almost quantitative yields and good enantioselectivities up to 86:14 e.r. under mild reaction conditions.
- Enders, Dieter,Rembiak, Andreas,Seppelt, Matthias
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supporting information
p. 470 - 473
(2013/02/23)
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- Asymmetric hydrogenation of N-alkyl and N-aryl ketimines using chiral cationic Ru(diamine) complexes as catalysts: The counteranion and solvent effects, and substrate scope
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Asymmetric hydrogenation of N-alkyl and N-aryl ketimines catalyzed by chiral cationic η6-arene-(N-monosulfonylated diamine) Ru(II) complexes has been investigated. Strong counteranion and solvent effects on the enantioselectivity were observed. The ruthenium catalyst bearing non-coordinating BArF- anion was found to be particularly effective for the hydrogenation of acyclic and exocyclic N-alkyl ketimines in the presence of (Boc)2O in dichloromethane or even under solvent-free conditions, providing chiral amines with up to >99% ee and full conversions. Alternatively, the ruthenium catalyst bearing achiral phosphate anion together with corresponding phosphoric acid as the additive was also efficient for the hydrogenation of N-alkyl ketimines in the absence of (Boc)2O with excellent enantioselectivities and full conversions. For N-aryl ketimines lower enantiomeric excesses were observed by using the ruthenium catalyst bearing BArF- anion. This catalytic protocol thus provides a facile and practical access to optically active amines and has been successfully employed in the gram-scale synthesis of enantiomerically pure (+)-sertraline.
- Chen, Fei,Ding, Ziyuan,He, Yanmei,Qin, Jie,Wang, Tianli,Fan, Qing-Hua
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supporting information; experimental part
p. 5248 - 5257
(2012/08/08)
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- Taking the F out of FLP: Simple lewis acid-base pairs for mild reductions with neutral boranes via borenium ion catalysis
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Discrete three-coordinate borenium salts 1c and 1d are accessed by cooperative Lewis acid-base pair-mediated heterolytic splitting of the B-H bond in pinacolborane by B(C6F5)3DABCO and Ph 3C+/DABCO, respectively. The resulting salts are competent catalysts in the reduction of a broad range of imines and can be generated in situ. Moreover, a mechanistic framework for borenium catalysis based on experimental evidence is proposed. The reaction is suggested to proceed by borenium activation of the imine substrate followed by counterintuitive hydride delivery from HBPin (with the assistance of DABCO) rather than from the HB(C6F5)3- anion, contrary to typical mechanisms of reduction in FLP systems.
- Eisenberger, Patrick,Bailey, Adrian M.,Crudden, Cathleen M.
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p. 17384 - 17387
(2013/01/15)
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- Comparison of decamethyldizincocene [(η5-Cp*) 2Zn2] versus decamethylzincocene [Cp*2Zn] and diethylzinc Et2Zn as precatalysts for the intermolecular hydroamination reaction
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A comparison of the Zn-Zn bonded species [(η5-Cp*) 2Zn2] versus the related organometallic zinc compound [Cp*2Zn] and ZnEt2 for the intermolecular hydroamination reaction in the presence of equimolar
- Luehl, Anja,Hartenstein, Larissa,Roesky, Peter W.,Blechert, Siegfried
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p. 7109 - 7116,8
(2020/09/02)
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- Montmorillonite as a heterogeneous catalyst in the efficient, mild and one pot synthesis of Schiff bases under solvent-free conditions
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A mild and efficient method has been reported for preparation of Schiff base ligands through condensation reaction of various aromatic aldehydes and ketones with different aromatic amines in the presence of montmorillonite as a heterogeneous catalyst under solvent free conditions. The advantages of this friendly, economically, environmentally and mild method are such as; simplicity of the reaction procedure, reusability of catalyst, simple work-up, high product yields and very short reaction times.
- Naeimi, Hossein,Rabiei, Khadijeh
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experimental part
p. 208 - 212
(2012/07/03)
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- Hydrogen activation by 2-boryl-N,N-dialkylanilines: A revision of Piers' ansa-aminoborane
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Two 2-[bis(pentafluorophenyl)boryl]-N,N-dialkylanilines reported here exemplify a new class of intramolecular frustrated B/N Lewis pairs. A structure closely related to this class structure was synthesized in 2003 by Piers et al. but was unable to activate H2. The new aminoboranes can activate hydrogen at near ambient conditions; besides, one of them can hydrogenate imines and enamines in a catalytic fashion demonstrating the validity of the original Piers' approach to hydrogen activation with ansa-aminoboranes.
- Chernichenko, Konstantin,Nieger, Martin,Leskelae, Markku,Repo, Timo
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supporting information; body text
p. 9029 - 9032
(2012/09/08)
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- Asymmetric hydrogenation of N-Alkyl ketimines with phosphine-free, chiral, cationic Ru-MsDPEN catalysts
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(Solvent) free and easy: A phosphine-free, chiral, cationic Ru-MsDPEN complex [(S,S)-1] is found to be an efficient catalyst for the enantioselective hydrogenation of a range of often-problematic N-alkyl ketimines (see scheme). This new method provides a more practical and greener synthetic approach to optically active amines, particularly N-alkyl amines, such as Sertraline.
- Chen, Fei,Wang, Tianli,He, Yanmei,Ding, Ziyuan,Li, Zhiwei,Xu, Lijin,Fan, Qing-Hua
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supporting information; experimental part
p. 1109 - 1113
(2011/03/21)
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- Activation of the Si-B Linkage: Copper-Catalyzed addition of nucleophilic silicon to imines
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Activation of the Si-B bond through copper-catalyzed transmetalation quickly developed into a practical method to generate Cu-Si reagents These silicon nucleophiles cleanly add to aldehyde-derived imine electrophiles to form R-silylated amines in protic media, and no carbon-tonitrogen Brook-type rearrangement of the intermediate anion is observed. Aside from electron-withdrawing groups at the imine nitrogen atom, for example, SO2Tol and P(O)Ph2, previously delicate nitrogen substituents such as phenyl or benzhydryl are tolerated. The same protocol also allows the unprecedented addition to representative ketone-derived imines.
- Vyas, Devendra J.,Froehlich, Roland,Oestreich, Martin
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supporting information; experimental part
p. 2094 - 2097
(2011/06/22)
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- Indium catalyzed tandem hydroamination/hydroalkylation of terminal alkynes
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The first direct intermolecular hydroamination/hydroalkylation of terminal alkynes catalyzed by In(OTf)3 under one-pot conditions leading to the formation of conjugated ketimines in good yields is described.
- Sarma, Rupam,Prajapati, Dipak
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scheme or table
p. 9525 - 9527
(2011/10/01)
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- Enantioselective construction of bridged multicyclic skeletons: Intermolecular [2+2+2] cycloaddition/intramolecular diels-alder reaction cascade
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Bridging a gap: A cationic rhodium(I)/ligand complex catalyzes the title reaction of alkynes and amide-linked 1,5-dienes, leading to bridged multicyclic compounds, with high chemo-, regio-, and enantioselectivity (see scheme; Bn=benzyl).
- Kobayashi, Masayuki,Suda, Takeshi,Noguchi, Keiichi,Tanaka, Ken
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supporting information; experimental part
p. 1664 - 1667
(2011/03/22)
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- Trifluoromethanesulfonic acid as an efficient catalyst in the reduction of ketimines
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Trifluoromethanesulfonic acid was found to be highly efficient catalyst in the reduction of ketimines with Hantzsh esters as the hydrogen source. The catalyst loading could be decreased to 1 mol %. Moderate to excellent isolated yields (up to 99 %) were obtained under mild conditions.
- Li, Jianhui,Wang, Zhouyu,Jiang, Zhenju,Jiang, Shengqian
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experimental part
p. 3101 - 3103
(2012/01/06)
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- Rhenium-catalyzed diastereoselective synthesis of aminoindanes via the insertion of allenes into a C-H bond
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Figure Presented. Aminoindane derivatives were synthesized diastereoselectively by the treatment of aromatic imines with allenes in the presence of a catalytic amount of a rhenium complex, [HRe(CO)4] n. The allenes inserted into the
- Kuninobu, Yoichiro,Yu, Peng,Takai, Kazuhiko
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supporting information; experimental part
p. 4274 - 4276
(2010/11/24)
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- Microwave-assisted, Pd(0)-catalyzed cross-coupling of diazirines with aryl halides
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Pd(0)-catalyzed cross-coupling reactions of diazirines with aryl halides under microwave heating conditions afford a series of substituted olefins. A reaction mechanism involving the migratory insertion of the Pd carbene intermediate is proposed.
- Zhao, Xia,Wu, Guojiao,Yan, Chong,Lu, Kui,Li, Hui,Zhang, Yan,Wang, Jianbo
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supporting information; experimental part
p. 5580 - 5583
(2011/02/23)
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- Modular synthesis of indoles from imines and o-dihaloarenes or o-chlorosulfonates by a Pd-catalyzed cascade process
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A detailed study of the scope of a new Pd-catalyzed synthesis of indolesfrom 1,2-dihaloarenes and o-halobenzene sulfonates and imines is descri bed. The cascade reaction comprises an imine a-arylation ollowed by an intramolecular C-N bond-forming reaction promoted by the same Pd catalyst. The reaction with 1,2-dibromobenzene shows wide scope and allows the introduction of aryl, alkyl, and vinyl substituents at different positions of the five-membered ring of the indole. The regioselective synthesis of indoles substituted in the six-membered ring can be carried out by employing o-dihalobenzene derivatives with two different halogens, taking advantage of the different reactivities of I, Br, and Cl in oxidative addition reactions. This paper also introduces a method for the efficient cleavage of the N-t-butyl group, thus allowing for the preparation of N-H indoles through the same methodology. Finally, the reaction with o-halosulfonates has been studied. The best substrates are o-chlorononaflates, which lead to indoles in very high yield. The reaction is particularlyappropriate for the synthesis of the challenging 6-substituted indoles. In view of the availability of o-chlorophenols, which are direct precur sors of the chlorononaflates, this reaction represents an efficient entry into indoles substituted in the six-membered ring. The concept is illustrated by the preparation of a 4,6-disubstituted indole from naturally occurring anethole.
- Barluenga, Jose,Jimenez-Aquino, Agustin,Aznar, Fernando,Valdes, Carlos
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supporting information; experimental part
p. 4031 - 4041
(2009/09/04)
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- 1,1′-Binaphthyldiamine-based lewis bases as readily available and efficient grganocatalysts for the reduction of N-Aryl and N-Alkyl ketimines
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The development of simple, low-cost, efficient, and sustainable routes to enantiomerically pure amines is a topic of extraordinary interest, specially in view of future industrial applications. In this context, we wish to report a chemical and stereochemical efficient synthesis of chiral amines through the Lewis base activated trichlorosilane reduction of ketimines. An organocatalyst, easily prepared in a single step through the condensation of picolinic acid and commercially available 1,1′-binaphthyldiamine, is the key element of this metal-free methodology, that allowed the synthesis of chiral secondary and primary amines in high yields and stereose-lectivity. Noteworthy, such catalysts are able to promote the reduction of N-alkyl ketimines, often in quantitative yield and up to 87% enantioselectivity; it: is worth mentioning that for such transformations only one other organocatalytic system has been reported so far.
- Guizzett, Stefania,Benaglia, Maurizio,Celentano, Giuseppe
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experimental part
p. 3683 - 3687
(2009/12/03)
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- Highly stereoselective metal-free catalytic reduction of Lmines: An easy entry to enantiomerically pure amines and natural And Unnatural α-amino esters
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A highly efficient catalytic stereoselective ketlmlne reduction is described. The combination of an Inexpensive chiral organocatalyst, easily prepared In a single step, and of a very cheap removable chiral auxiliary allowed us to obtain enantlomerlcally pure amino compounds. The methodology allowed synthesis of chiral secondary and primary amines and natural and unnatural amino esters In high yields often with total control of the absolute stereochemistry.
- Gulzzettl, Stefania,Benagila, Maurizio,Rossi, Sergio
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supporting information; experimental part
p. 2928 - 2931
(2009/12/05)
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- Chiral Lewis base promoted trichlorosilane reduction of ketimines. An enantioselective organocatalytic synthesis of chiral amines
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The reduction of the carbon-nitrogen double bond is an important transformation. Here we report our studies on a family of chiral organic catalysts able to promote the stereoselective reduction of ketimines with trichlorosilane. The very cheap, metal-free catalysts were easily prepared in one step from commercially available products, namely a chiral aminoalcohol and picolinic acid derivatives. The catalyst structure was extensively modified in a study that allowed to identify an extremely active species, able to promote the reduction on a large variety of substrates with high efficiency (up to 95% ee). A three component methodology has been also developed, where the enantiomerically enriched amine was isolated after performing the reaction by mixing a ketone and an amine in the presence of trichlorosilane and the catalyst. Its synthetic potentiality was demonstrated by employing the present metal-free catalytic procedure in the preparation of (S)-metolachlor, a potent and widely used herbicide.
- Guizzetti, Stefania,Benaglia, Maurizio,Cozzi, Franco,Annunziata, Rita
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experimental part
p. 6354 - 6363
(2010/01/06)
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- A highly enantioselective organocatalytic method for reduction of aromatic N-alkyl ketimines
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A study has demonstrated the development of a highly enantioselective catalytic method for the reduction of aromatic N-alkyl ketimines by trichlorosilane under mild conditions using the newly designed Lewis base organocatalyst that incorporates C- and S-chirality. The S-chiral sulfinamide group in these catalysts plays a crucial role similar to the carboxamide groups as Lewis base for the activation of HSiCl3, and also serves as a source of chirality that the carboxamide group lacks for the asymmetric induction. The results of the study showed that excellent enantioselectivities of up to 99.6% ee and high yields were obtained for a wide range of substrates. Further works is also in progress to clarify the mechanism of the transformation and explore the full application scope of the present catalyst system.
- Wang, Chao,Wu, Xinjun,Zhou, Li,Sun, Jian
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supporting information; experimental part
p. 8789 - 8792
(2009/09/25)
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- Facile and efficient method for preparation of Schiff bases catalyzed by P2O5/SiO2 under free Solvent conditions
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A simple and convenient method for the preparation of Schiff bases is developed. In this method, the Schiff base compounds were prepared from the reaction of carbonyl compounds with primary amines. In this reaction, P 2O5/SiO2 have catalyzed the Schiff base formation in dry media under solvent-free conditions. Advantages of this method are use of an inexpensive and efficient catalyst, high yields of products, short reaction times, and simplicity of the reaction and workup.
- Naeimi, Hossein,Sharghi, Hashem,Salimi, Fariba,Rabiei, Khadijeh
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- Solvent-free synthesis of racemic α-aminonitriles
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A very simple one-step, environmentally friendly procedure for the synthesis of α-aminonitriles from aldehydes and ketones, using trimethylsilyl cyanide in the absence of solvent, is reported. The active catalyst of this three-component (Strecker) reaction was the amine employed in the transformation. In general, aldehydes react more rapidly than ketones and give almost quantitative yields of the corresponding α-aminonitriles in less than fifteen minutes. However, only cyclic ketones afford the corresponding α-aminonitriles in excellent chemical yields under these conditions. Georg Thieme Verlag Stuttgart.
- Baeza, Alejandro,Najera, Carmen,Sansano, Jose M.
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p. 1230 - 1234
(2008/02/02)
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- The simple and selective synthesis of 3-amino-2,2-difluorocarboxylic esters and difluoro-β-lactams using ethyl bromodifluoroacetate in the presence of rhodium catalyst
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Treatment of imines (5) with ethyl bromodifluoroacetate (1) and Et 2Zn in the presence of RhCl(PPh3)3 in anhydrous medium gave difluoro-β-lactams (7) in good to excellent yields, while 3-amino-2,2-difluorocarboxylic esters (6) were obtained in good yields by adding MgSO4·7H2O to the reaction medium.
- Sato, Kazuyuki,Tarui, Atsushi,Matsuda, Seiji,Omote, Masaaki,Ando, Akira,Kumadaki, Itsumaro
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p. 7679 - 7681
(2007/10/03)
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- Reductive amination of aldehydes and ketones with sodium borohydride supported onto HZSM-5 zeolite under microwave irradiation in a solvent free system
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Sodium borohydride supported onto a HZSM-5 zeolite is presented as a general reducing agent for the reductive amination of aldehydes and ketones under microwave irradiation in solventless system. Copyright Taylor & Francis Inc.
- Oskooie, Hossein A.,Amiri, Somaih Solemani,Heravi, Majid M.,Ghassemzadeh, Mitra
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p. 2047 - 2050
(2007/10/03)
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- Role of noncovalent interactions in the enantioselective reduction of aromatic ketimines with trichlorosilane
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Asymmetric reduction of ketimines 1 with trichlorosilane can be catalyzed by a new N-methyl L-valine derived Lewis basic organocatalyst, such as 4d, with high enantioselectivity. The structure-reactivity investigation suggests hydrogen bonding and arene-arene interactions between the catalyst and the incoming imine as the main factor determining the enantiofacial selectivity.
- Malkov, Andrei V.,Mariani, Andrea,MacDougall, Kenneth N.,Kocovsky, Pavel
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p. 2253 - 2256
(2007/10/03)
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- Application of monodentate secondary phosphine oxides, a new class of chiral ligands, in Ir(I)-catalyzed asymmetric imine hydrogenation
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(Matrix presented) Secondary phosphine oxides were prepared from R 1PCl2 and R2MgBr, followed by hydrolysis. They were obtained in an enantiopure form by preparative chiral HPLC. These new monodentate ligands were tested in the iridium-catalyzed hydrogenation of imines at 25 bar. Enantioselectivities up to 76% were obtained at L/lr = 2. Addition of pyridine (Pyr/lr = 1:2) raised the ee to 83%. Using pyridine as an additive allowed reduction of the L/lr ratio to 1 without reduction of ee.
- Jiang, Xiao-Bin,Minnaard, Adriaan J.,Hessen, Bart,Feringa, Ben L.,Duchateau, Alexander L. L.,Andrien, Jean G. O.,Boogers, Jeroen A. F.,De Vries, Johannes G.
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p. 1503 - 1506
(2007/10/03)
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- Reduction and reductive coupling of imines by Sm(II)-based reagents
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The reductive coupling of aldimines and ketimines by a series of Sm(II)-based reagents (SmI2, SmI2-HMPA, SmBr2, Sm{N[Si(CH3)3]2}2, and SmI 2/triethylamine/water) were examined. In general, aldimines and ketimines were efficiently reduced or coupled using reductants that are more powerful than SmI2, and the use of Sm{N[Si(CH3) 3]2}2 led to higher diastereoselectivities in reductive coupling reactions. Surprisingly, only the combination of SmI 2/triethylamine/water was capable of reducing and coupling para-substituted benzaldimines and coupling ketimines.
- Kim, Myeongseob,Knettle, Brian W.,Dahlén, Anders,Hilmersson, G?ran,Flowers II, Robert A.
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p. 10397 - 10402
(2007/10/03)
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- Method for preparing chiral diphosphines
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The invention concerns a method for preparing a compound of formula (1) wherein: A represents naphthyl or phenyl optionally substituted; and Ar1, Ar2independently represent a saturated or aromatic carbocyclic group, optionally substituted.
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- A simple protocol for direct reductive amination of aldehydes and ketones using potassium formate and catalytic palladium acetate
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A method for direct reductive amination of aldehydes and ketones, including α,β-unsaturated carbonyl compounds, has been developed, which requires potassium formate as reductant and palladium acetate as catalyst. Suitable amines include both primary and secondary aliphatic and aromatic amines.
- Basu, Basudeb,Jha, Satadru,Bhuiyan, Md. Mosharef H.,Das, Pralay
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p. 555 - 557
(2007/10/03)
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