- Stereo- and Chemo-Selectivity in reduction of α-alkyl Aryl Ketones with Metal Hydrides
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Metal hydride reduction of a variety of α-alkyl aryl ketones gives a mixture of threo- and erythro-β-aryl-β-hydroxyalkyl phenyl(or methyl)selenides by carbonyl reduction and 1-aryl-1-alkanol by the substitution of a phenyl(or methyl)seleno group with hydrogen.With all metal hydrides examined the formation of the threo-isomer always predominated.The addition of various metal chlorides in the reduction of various α-heteroatom (N, P, O, S)-substituted ketones.
- Aoki, Ikuo,Nishibayashi,Uemura, Sakae
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- Copper-Catalyzed Enantioconvergent Cross-Coupling of Racemic Alkyl Bromides with Azole C(sp2)?H Bonds
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The development of enantioconvergent cross-coupling of racemic alkyl halides directly with heteroarene C(sp2)?H bonds has been impeded by the use of a base at elevated temperature that leads to racemization. We herein report a copper(I)/cinchona-alkaloid-derived N,N,P-ligand catalytic system that enables oxidative addition with racemic alkyl bromides under mild conditions. Thus, coupling with azole C(sp2)?H bonds has been achieved in high enantioselectivity, affording a number of potentially useful α-chiral alkylated azoles, such as 1,3,4-oxadiazoles, oxazoles, and benzo[d]oxazoles as well as 1,3,4-triazoles, for drug discovery. Mechanistic experiments indicated facile deprotonation of an azole C(sp2)?H bond and the involvement of alkyl radical species under the reaction conditions.
- Chang, Xiao-Yong,Chen, Ji-Jun,Gu, Qiang-Shuai,Jiang, Sheng-Peng,Li, Zhong-Liang,Liu, Lin,Liu, Xiao-Dong,Liu, Xin-Yuan,Su, Xiao-Long,Wang, Fu-Li,Yang, Chang-Jiang,Ye, Liu
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supporting information
p. 380 - 384
(2020/10/30)
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- Homoleptic cobalt(II) phenoxyimine complexes for hydrosilylation of aldehydes and ketones without base activation of cobalt(II)
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Air-stable, easy to prepare, homoleptic cobalt(II) complexes bearing pendant-modified phenoxyimine ligands were synthesized and determined. The complexes exhibited high catalytic performance for reducing aldehydes and ketones via catalytic hydrosilylation, where a hydrosilane and a catalytic amount of the cobalt(II) complex were added under base-free conditions. The reaction proceeded even in the presence of excess water, and excellent functional-group tolerance was observed. Subsequent hydrolysis gave the alcohol in high yields. Moreover, H2O had a critical role in activation of the Co(II) catalyst with hydrosilane. Several additional results also indicated that the cobalt(II) center acts as an active catalyst in the hydrosilylation of aldehydes and ketones.
- Hori, Momoko,Ishikawa, Ryuta,Koga, Yuji,Matsubara, Kouki,Mitsuyama, Tomoaki,Shin, Sayaka
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p. 1379 - 1387
(2021/05/29)
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- Regiodivergent Hydroborative Ring Opening of Epoxides via Selective C-O Bond Activation
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A magnesium-catalyzed regiodivergent C-O bond cleavage protocol is presented. Readily available magnesium catalysts achieve the selective hydroboration of a wide range of epoxides and oxetanes yielding secondary and tertiary alcohols in excellent yields and regioselectivities. Experimental mechanistic investigations and DFT calculations provide insight into the unexpected regiodivergence and explain the different mechanisms of the C-O bond activation and product formation.
- Magre, Marc,Paffenholz, Eva,Maity, Bholanath,Cavallo, Luigi,Rueping, Magnus
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supporting information
p. 14286 - 14294
(2020/09/15)
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- COMPOUNDS, COMPOSITIONS, AND METHODS OF USE
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Described herein are compounds that act as CYP46A1 inhibitors, compositions comprising these compounds, and methods of their use into treating neurodegenerative diseases and the like, or a pharmaceutically active salt thereof. The present invention relates to compounds represented by the formula wherein each symbol is as defined in the specification, or a pharmaceutically active salt thereof.
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Paragraph 0259
(2020/12/11)
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- Efficient Transfer Hydrogenation of Ketones using Methanol as Liquid Organic Hydrogen Carrier
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Herein, we demonstrate an efficient protocol for transfer hydrogenation of ketones using methanol as practical and useful liquid organic hydrogen carrier (LOHC) under Ir(III) catalysis. Various ketones, including electron-rich/electron-poor aromatic ketones, heteroaromatic and aliphatic ketones, have been efficiently reduced into their corresponding alcohols. Chemoselective reduction of ketones was established in the presence of various other reducible functional groups under mild conditions.
- Garg, Nidhi,Paira, Soumen,Sundararaju, Basker
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p. 3472 - 3476
(2020/05/29)
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- Potassium Fluoride-Catalyzed Hydroboration of Aldehydes and Ketones: Facile Reduction to Primary and Secondary Alcohols
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A catalytic hydroboration of various ketones and aldehydes can be achieved in the presence of inexpensive and commercially available inorganic salts containing fluoride anion. As a result, the reduction of carbonyl moieties to the corresponding primary and secondary alcohols can be achieved at room temperature under mild conditions.
- Kuciński, Krzysztof,Hreczycho, Grzegorz
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p. 552 - 555
(2020/02/04)
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- Observation of hyperpositive non-linear effect in catalytic asymmetric organozinc additions to aldehydes
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Asymmetric amplification is a phenomenon that is believed to play a key role in the emergence of homochirality in life. In asymmetric catalysis, theoretical and experimental models have been investigated to provide an understanding of how chiral amplification is possible, in particular based on non-linear effects. Interestingly, it has been proposed a quarter century ago that chiral catalysts, when not enantiopure might even be more enantioselective than their enantiopure counterparts. We show here that such hyperpositive non-linear effect in asymmetric catalysis is indeed possible. An in-depth study into the underlying mechanism was carried out, and the scheme we derive differs from the previous proposed models.
- Geiger, Yannick,Achard, Thierry,Maisse-Fran?ois, Aline,Bellemin-Laponnaz, Stéphane
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supporting information
p. 1250 - 1256
(2020/07/25)
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- Lithium triethylborohydride as catalyst for solvent-free hydroboration of aldehydes and ketones
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Commercially available and inexpensive lithium triethylborohydride (LiHBEt3) acts as efficient catalyst for the solvent-free hydroboration of a wide range of aldehydes and ketones, which were subsequently transformed to corresponding 1° and 2° alcohols in one-pot procedure at room temperature (rt).
- Kuciński, Krzysztof,Hreczycho, Grzegorz
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p. 1912 - 1915
(2019/04/27)
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- Supramolecular Interlocked Biphenyl Ligands for Enantioselective Ti-Catalyzed Alkylation of Aromatic Aldehydes
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The substitution of tropos 2,2′-biphenols with (S)-amino-acid-derived interaction sites in the 5,5′-position results in a spontaneous desymmetrization. This process is driven by well-defined intermolecular hydrogen bonding, which leads to diastereoselecti
- Scholtes, Jan Felix,Trapp, Oliver
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supporting information
p. 3955 - 3960
(2019/07/03)
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- Ni-Catalyzed β-Alkylation of Cyclopropanol-Derived Homoenolates
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Metal homoenolates are valuable synthetic intermediates which provide access to β-functionalized ketones. In this report, we disclose a Ni-catalyzed β-alkylation reaction of cyclopropanol-derived homoenolates using redox-active N-hydroxyphthalimide (NHPI) esters as the alkylating reagents. The reaction is compatible with 1°, 2°, and 3° NHPI esters. Mechanistic studies imply radical activation of the NHPI ester and 2e β-carbon elimination occurring on the cyclopropanol.
- Mills, L. Reginald,Zhou, Cuihan,Fung, Emily,Rousseaux, Sophie A. L.
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supporting information
p. 8805 - 8809
(2019/11/03)
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- Chiral 2-(2-hydroxyaryl)alcohols (HAROLs) with a 1,4-diol scaffold as a new family of ligands and organocatalysts
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Efficient and modular syntheses of chiral 2-(2-hydroxyaryl)alcohols (HAROLs), novel 1,4-diols carrying one phenolic and one alcohol hydroxyl group, have been developed which led to generation of a small library of structurally diverse HAROLs in enantiomerically pure form. Of the different HAROLs examined, a HAROL based on the indan backbone exhibited the highest activity and enantioselectivity in the 1,2-addition of certain organometallic compounds to aldehydes in the presence of Ti(OiPr)4 (up to 97% y, 88% ee) and performed as a hydrogen-bond donor organocatalyst in the Morita-Baylis-Hillman reaction, promoted by trialkylphosphines.
- Dilek, ?mer,Tezeren, Mustafa A.,Tilki, Tahir,Ertürk, Erkan
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supporting information
p. 268 - 286
(2017/12/06)
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- New C2-symmetric six-membered carbene ligands for asymmetric diethylzinc addition of arylaldehydes
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A series of new six-membered NHC precursors were prepared by simply esterification of their parent compounds. Their applicability in asymmetric diethylzinc addition of arylaldehydes has been demonstrated and the corresponding secondary alcohol was obtained with good yields and moderate enantioselectivities. (Figure pressented)
- Zhou, Bihui,Li, Zijing,Yang, Chen,Li, Linlin,Fan, Limei,Huang, Hongxia,Li, Jie
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- Noscapine Derivatives as New Chiral Catalysts in Asymmetric Synthesis: Highly Enantioselective Addition of Diethylzinc to Aldehydes
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Noscapine, a natural alkaloid, has never been used as a parent scaffold in chiral induction. The first examples of noscapinoid compounds as efficient catalysts in asymmetric synthesis are now reported. Three derivatives of noscapine were synthesized from its reaction with different Grignard reagents. Asymmetric addition of diethylzinc to aldehydes was performed in the presence of these catalysts in high yields and good to excellentees.
- Mohebbi, Maryam,Bararjanian, Morteza,Ebrahimi, Samad N.,Smie?ko, Martin,Salehi, Peyman
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p. 1841 - 1848
(2018/02/14)
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- Pure phosphotriesters as versatile ligands in transition metal catalysis: efficient hydrosilylation of ketones and diethylzinc addition to aldehydes
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This work aims to highlight the underrated role played by pure phosphotriester (or phosphate) ligands in catalysis, when compared to other phosphorus-containing donors such as phosphane oxides or phosphites. To probe this and to enlarge the very narrow catalytic scope of these Lewis bases, easily accessible mono- and bidentate phosphotriesters were tested as donors in two important transition metal-based catalytic transformations: the zinc-catalyzed hydrosilylation of ketones and the titanium-promoted diethylzinc addition to aldehydes. In both cases, the reactions were successful and the corresponding alcohols were obtained in high yields.
- Bouhachicha,Ngo Ndimba,Roisnel,Lalli,Argouarch
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p. 4767 - 4770
(2017/07/11)
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- Exploring Tandem Ruthenium-Catalyzed Hydrogen Transfer and SNAr Chemistry
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A hydrogen-transfer strategy for the catalytic functionalization of benzylic alcohols via electronic arene activation, accessing a diverse range of bespoke diaryl ethers and aryl amines in excellent isolated yields (38 examples, 70% average yield), is reported. Taking advantage of the hydrogen-transfer approach, the oxidation level of the functionalized products can be selected by judicious choice of simple and inexpensive additives.
- Polidano, Kurt,Reed-Berendt, Benjamin G.,Basset, Ana?s,Watson, Andrew J. A.,Williams, Jonathan M. J.,Morrill, Louis C.
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supporting information
p. 6716 - 6719
(2017/12/26)
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- Manganese complex-catalyzed oxidation and oxidative kinetic resolution of secondary alcohols by hydrogen peroxide
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The highly efficient catalytic oxidation and oxidative kinetic resolution (OKR) of secondary alcohols has been achieved using a synthetic manganese catalyst with low loading and hydrogen peroxide as an environmentally benign oxidant in the presence of a small amount of sulfuric acid as an additive. The product yields were high (up to 93%) for alcohol oxidation and the enantioselectivity was excellent (>90% ee) for the OKR of secondary alcohols. Mechanistic studies revealed that alcohol oxidation occurs via hydrogen atom (H-atom) abstraction from an α-CH bond of the alcohol substrate and a two-electron process by an electrophilic Mn-oxo species. Density functional theory calculations revealed the difference in reaction energy barriers for H-atom abstraction from the α-CH bonds of R- and S-enantiomers by a chiral high-valent manganese-oxo complex, supporting the experimental result from the OKR of secondary alcohols.
- Miao, Chengxia,Li, Xiao-Xi,Lee, Yong-Min,Xia, Chungu,Wang, Yong,Nam, Wonwoo,Sun, Wei
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p. 7476 - 7482
(2017/10/30)
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- Halogen-bonded iodonium ion catalysis: A route to α-hydroxy ketones: Via domino oxidations of secondary alcohols and aliphatic C-H bonds with high selectivity and control
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A domino synthesis of α-hydroxy ketones has been developed from benzylic secondary alcohols employing catalytic iodonium ions stabilized by DMSO. The reaction proceeds through an unprecedented sequential oxidation of alcohols to ketone and its α-hydroxylation in a controlled manner. The spectroscopic evidence establishes the possibility of formation of a stable halogen-bonded adduct between DMSO and iodonium ions.
- Guha, Somraj,Kazi, Imran,Mukherjee, Pranamita,Sekar, Govindasamy
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supporting information
p. 10942 - 10945
(2017/10/13)
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- Bu4NI-Catalyzed α-Oxyacylation of Carbonyl Compounds with Toluene Derivatives
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A TBAI (tetrabutylammonium iodide)-catalyzed direct α-oxyacylation of carbonyl compounds from readily available toluene derivatives has been developed. The distinguished features of this metal-free protocol include the employment of simple starting material, a wide carbonyl compound scope, and mild reaction conditions.
- Li, Chengliang,Jin, Tao,Zhang, Xinglu,Li, Chunju,Jia, Xueshun,Li, Jian
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supporting information
p. 1916 - 1919
(2016/05/19)
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- Design and synthesis of orally bioavailable 4-methyl heteroaryldihydropyrimidine based hepatitis B virus (HBV) capsid inhibitors
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Targeting the capsid protein of hepatitis B virus (HBV) and thus interrupting normal capsid formation have been an attractive approach to block the replication of HBV viruses. We carried out multidimensional structural optimizations based on the heteroaryldihydropyrimidine (HAP) analogue Bay41-4109 (1) and identified a novel series of HBV capsid inhibitors that demonstrated promising cellular selectivity indexes, metabolic stabilities, and in vitro safety profiles. Herein we disclose the design, synthesis, structureactivity relationship (SAR), cocrystal structure in complex with HBV capsid proteins and in vivo pharmacological study of the 4-methyl HAP analogues. In particular, the (2S,4S)-4,4-difluoroproline substituted analogue 34a demonstrated high oral bioavailability and liver exposure and achieved over 2 log viral load reduction in a hydrodynamic injected (HDI) HBV mouse model.
- Qiu, Zongxing,Lin, Xianfeng,Zhou, Mingwei,Liu, Yongfu,Zhu, Wei,Chen, Wenming,Zhang, Weixing,Guo, Lei,Liu, Haixia,Wu, Guolong,Huang, Mengwei,Jiang, Min,Xu, Zhiheng,Zhou, Zheng,Qin, Ning,Ren, Shuang,Qiu, Hongxia,Zhong, Sheng,Zhang, Yuxia,Zhang, Yi,Wu, Xiaoyue,Shi, Liping,Shen, Fang,Mao, Yi,Zhou, Xue,Yang, Wengang,Wu, Jim Z.,Yang, Guang,Mayweg, Alexander V.,Shen, Hong C.,Tang, Guozhi
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p. 7651 - 7666
(2016/09/04)
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- Chemo- and Enantioselective Addition and β-Hydrogen Transfer Reduction of Carbonyl Compounds with Diethylzinc Reagent in One Pot Catalyzed by a Single Chiral Organometallic Catalyst
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Using a single chiral phosphoramide-Zn(II) complex as the catalyst, the asymmetric β-H transfer reduction of aromatic α-trifluoromethyl ketones and enantioselective addition of aromatic aldehydes with Et2Zn in one pot were successfully realized, affording the corresponding additive products of secondary alcohols in high yields (up to 99%) with excellent enantioselectivities (up to 98% ee) and the reduction products of α-trifluoromethyl alcohols in good to excellent yields with up to 77% ee.
- Huang, Huayin,Zong, Hua,Bian, Guangling,Song, Ling
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p. 12614 - 12619
(2016/01/09)
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- DMF Dimethyl Acetal as Carbon Source for α-Methylation of Ketones: A Hydrogenation-Hydrogenolysis Strategy of Enaminones
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A novel heterogeneous catalytic hydrogenation-hydrogenolysis strategy has been developed for the α-methylation of ketones via enaminones using DMF dimethyl acetal as carbon source. This strategy provides a very convenient route to α-methylated ketones using a variety of ketones without any base or oxidant. (Chemical Equation Presented).
- Borah, Ashwini,Goswami, Limi,Neog, Kashmiri,Gogoi, Pranjal
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p. 4722 - 4728
(2015/05/13)
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- A catalytic system for the activation of diorganozinc reagents
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We report a novel catalytic system for the activation of diorganozinc reagents. We assumed that the nucleophilic activation of diethylzinc should be efficiently performed by simple alkali metal salts. Indeed, the combination of sodium salts and 15-crown-5 significantly accelerates the rate of diethylzinc addition to benzaldehyde under mild conditions. The activity of the catalytic system strongly depends on the nature of the anion, decreasing in the order I->Br->Cl->F-. Under the optimized reaction conditions, various aryl, hetero aryl, and aliphatic aldehydes were converted with diethylzinc and the corresponding product was obtained in excellent yields. The first X-ray absorption spectroscopy measurements on such type of reactions provide initial insights that support the proposed catalytic cycle and suggest the formation of a zincate complex.
- Werner, Thomas,Bauer, Matthias,Riahi, Abdol Majid,Schramm, Heiko
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p. 4876 - 4883
(2014/08/05)
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- A new pyrrolidine-derived atropisomeric amino alcohol as a highly efficient chiral ligand for the asymmetric addition of diethylzinc to aldehydes
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A highly efficient pyrrolidine-derived atropisomeric amino alcohol, (Sa)-1-[2-diphenylhydroxymethyl-6-(trifluoromethyl)phenyl]-2-(1-pyrrolido)methyl-1H-pyrrole, has been synthesized as a chiral ligand for the enantioselective addition of diethylzinc to some prochiral aldehydes to afford (S)-alcohols. The conversion rates were close to quantitative with good to excellent enantiomeric excesses (up to 95% ee).
- Faigl, Ferenc,Erdélyi, Zsuzsa,Deák, Szilvia,Nyerges, Miklós,Mátrav?lgyi, Béla
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supporting information
p. 6891 - 6894
(2015/02/02)
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- Chiral porous TADDOL-embedded organic polymers for asymmetric diethylzinc addition to aldehydes
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Two chiral porous organic polymers (CPOPs) were synthesized by linking a TADDOL-embedded building block with arylethynylenes units. The CPOPs are highly stable to thermal treatment, moisture, acidity, and basicity. The dihydroxy groups of TADDOL inside th
- Wang, Xiuren,Zhang, Jie,Liu, Yan,Cui, Yong
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p. 435 - 440
(2014/04/17)
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- Modular prolinol chiral ligands for enantioselective addition of diethylzinc to aromatic aldehydes
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Enantioselective addition of diethylzinc (ZnEt2) to a series of aromatic aldehydes was promoted using a modular prolinol chiral ligand, 2-(S)-2-(hydroxydiphenylmethyl)pyrrolidin-1-yl)methyl)-4-nitrophenol (1a), without using titanium complex. The catalytic system employing 15 mol% of 1a was found to promote the addition of diethylzinc to a wide range of aromatic aldehydes with electron-donating and electron-withdrawing substituents, giving up to 86% ee of the corresponding secondary alcohol under mild conditions.
- Gou, Shaohua,Ye, Zhongbin,Feng, Mingming,Jiang, Wenchao
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p. 941 - 950
(2013/02/25)
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- 2-Pyridylsulfinamides as effective catalysts in the asymmetric alkylation of aldehydes with diethylzinc Dedicated to Dr. N.N. Joshi, National Chemical Laboratory, Pune, India
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Chiral 2-pyridylsulfinamides were shown to be effective catalysts in the alkylation of aryl and alkyl aldehydes with diethylzinc providing the corresponding alcohols in excellent enantioselectivity. Sulfinamide catalysts possessing solitary chirality at the sulfur center produced the product phenethyl alcohol in good enantioselectivity. Diastereomeric sulfinamides possessing chirality at the carbon-bearing nitrogen and at the sulfur of the sulfinamide increased the enantioselectivity of the product alcohols up to >99%. However, there is no effect of the match-mismatch pair of sulfinamide diastereomers on the outcome of the chiral induction of the product phenethyl alcohols. It was conclusively proved that chirality at the sulfur center is mandatory for obtaining good enantioselectivity in the reaction.
- Prasad, Kavirayani R.,Revu, Omkar
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p. 8422 - 8428
(2013/09/02)
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- Asymmetric preparation of new N, N -dialkyl-2-amino-1,1,2-triphenylethanol catalysts and a kinetic resolution in the addition of diethylzinc to flavene-3-carbaldehydes
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Enantiopure N,N-dialkyl-(S)-2-amino-1,1,2-triphenylethanols were prepared using a new synthetic methodology and tested for their ability to catalyze the enantioselective addition of diethylzinc to aldehydes. The structural modification of N-substituents of the catalysts led us to identify N-methyl-N-(S)-1-phenyl-ethyl-substituted 4d as an effective catalyst for the addition. Also disclosed is a kinetic resolution of racemic flavene-3- carbaldehydes with the chiral catalyst.
- Kang, Seockyong,Baek, Jinho,Ko, Yikyung,Im, Chan,Park, Yongsun
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supporting information
p. 630 - 634
(2013/04/23)
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- Click-BINOLs: A new class of tunable ligands for asymmetric catalysis
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A new class of easily tunable 1,2,3-triazole-BINOL ligands, 'click'-BINOLs, have been synthesized from readily available alkynes and several azido-BINOL derivatives using the powerful Huisgen [3+2] cycloaddition 'click' approach. The activity of these ligands in asymmetric Lewis acid catalysis has been explored for the first time in the diethylzinc addition to aldehydes. The C 2-symmetric ligand 1d showed an interesting catalytic behavior, which suggests the non-innocent participation of the triazole units. Thus, good enantioselectivities (up to 86% ee) were obtained by both the right selection of the substitution pattern at the triazole ring and the fine tuning of the reaction conditions. Georg Thieme Verlag Stuttgart New York.
- Beckendorf, Stephan,Mancheno, Olga Garcia
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experimental part
p. 2162 - 2172
(2012/10/07)
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- Polystyrene-supported (2S)-(-)-3-exo-piperazinoisoborneol: An efficient catalyst for the batch and continuous flow production of enantiopure alcohols
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A polystyrene-supported analog (PS-PIB) of 3-exo-morpholinoisoborneol (MIB), designed for increased chemical stability, has been synthesized and used as a ligand in the asymmetric alkylation of aldehydes with Et2Zn. The supported ligand turned out to be highly active and enantioselective for a broad scope of substrates (92-99% ee), allowing repeated recycling. A single-pass, continuous flow process implemented with PS-PIB shows only a marginal decrease in conversion after 30 h of operation.
- Osorio-Planes, Laura,Rodriguez-Escrich, Carles,Pericas, Miquel A.
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supporting information; experimental part
p. 1816 - 1819
(2012/07/03)
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- Sugar-monophosphite ligands applied to the asymmetric Ni-catalyzed trialkylaluminum addition to aldehydes
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A series of readily available sugar-based phosphite ligands were applied to the Ni-catalyzed asymmetric trialkylaluminum additions to aldehydes. The ability of the catalysts to transfer chiral information to the product could be tuned by choosing suitable ligand components (configuration at C-3 of the furanoside backbone; the steric hindrance of the substituent at C-3 and the substituents/configuration of the biaryl phosphite moieties). Good enantioselectivities (ee's up to 84%) were obtained for several aryl aldehydes using several organoaluminum sources.
- Alegre, Sabina,Dieguez, Montserrat,Pmies, Oscar
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experimental part
p. 834 - 839
(2011/08/22)
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- Phosphonium salt catalyzed addition of diethylzinc to aldehydes
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The addition of diethylzinc to aromatic, heteroaromatic, and aliphatic aldehydes at room temperature is efficiently catalyzed by 1-7 mol% tetrabutylphosphonium chloride. The corresponding addition products are obtained in good to excellent yields of up to 99%. Moreover, polymer bond phosphonium salts can be used to catalyze this reaction with excellent recovery of the polymer bond catalyst up to three cycles. The application of chiral bifunctional phosphonium salts revealed a remarkable counter anion effect. Changing the anion, the activity of the tetrabutylphosphonium salt decreased in the order Cl- > Br- > I- ≈ TsO- > BF4- ≈ PF6-. However, the nature of the cation had also significant influence. Tetraalkyl-ammonium chlorides showed similar activity compared to phosphonium chlorides, while alkaline metal chlorides proved to be considerably less active. Georg Thieme Verlag Stuttgart.
- Werner, Thomas,Riahi, Abdol Majid,Schramm, Heiko
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experimental part
p. 3482 - 3490
(2011/12/04)
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- (R)-(+)-N-methylbenzoguanidine ((R)-NMBG) catalyzed kinetic resolution of racemic secondary benzylic alcohols with free carboxylic acids by asymmetric esterification
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(R)-(+)-N-Methylbenzoguanidine ((R)-NMBG) was found to function as an efficient acyl-transfer catalyst for the kinetic resolution of racemic secondary benzylic alcohols in the presence of achiral carboxylic acids and pivalic anhydride. The use of a tertiary amine in this reaction is not necessary to attain good chemical yields of the products. It was determined that diphenylacetic acid could be employed as the most suitable acyl donor for achieving a high enantioselectivity for the kinetic resolution of the racemic secondary benzylic alcohols having normal aliphatic alkyl chains at the C-1 positions. On the other hand, a less-hindered carboxylic acid, such as 3-phenylpropanoic acid, functioned as a better acyl donor for the kinetic resolution of racemic secondary benzylic alcohols having branched aliphatic alkyl chains at the C-1 positions.
- Nakata, Kenya,Shiina, Isamu
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supporting information; experimental part
p. 7092 - 7096
(2011/11/04)
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- Ar-BINMOLs with axial and sp3 central chirality - Characterization, chiroptical properties, and application in asymmetric catalysis
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2′-Hydroxy-1,1′-binaphthalene-2-(arylmethanol) (Ar-BINMOLs), a family of new 1,1′-binaphthalene-2,2′-diol derivatives, prepared by a [1,2]-Wittig rearrangement, are introduced as new chiral molecules for the study of the modes of supramolecular aggregatio
- Gao, Guang,Bai, Xing-Feng,Yang, Hua-Meng,Jiang, Jian-Xiong,Lai, Guo-Qiao,Xu, Li-Wen
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supporting information; experimental part
p. 5039 - 5046
(2011/10/09)
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- Modular amino acid amide chiral ligands for enantioselective addition of diethylzinc to aromatic aldehydes
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Enantioselective addition of diethylzinc to a series of aromatic aldehydes was developed using a modular amino acid amide chiral ligand (2S)-3-phenyl-N-((R)-1-phenyl-ethyl)-2-(tosylamino)propanamide without using titanium complex. The catalytic system employing 10 mol% of 1g was found to promote the addition of diethylzinc (ZnEt2) to a wide range of aromatic aldehydes with electron-donating and electron-withdrawing substituents, giving up to 82% ee of the corresponding secondary alcohol under mild conditions.
- Gou, Shaohua,Ye, Zhongbin,Chang, Jing,Gou, Guangjun,Feng, Mingming
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experimental part
p. 448 - 453
(2012/02/03)
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- A systematic study of chiral homoprolinols and their derivatives in the catalysis of enantioselective addition of diethylzinc to aldehydes
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Homoprolinol analogs, a class of optically active γ-amino alcohols, were examined systematically in the enantioselective addition reactions of diethylzinc to aldehydes. By comparison of the results catalyzed by these γ-amino alcohols with those by the β-amino alcohols based on pyrrolidine architecture reported in the literature references, we have observed that the γ-amino alcohols are superior to the corresponding β-amino alcohols when the nitrogen and the oxygen are unsubstituted. Among the homoprolinols we tested, 2b gave the best results (45-88% yields, 44-81% ee) in the addition reactions. To the best of our knowledge, 2b has been noticed as one of the most efficient γ-amino alcohol catalysts based on pyrrolidine framework.
- Liu, Chang-Lu,Wei, Chang-Yong,Wang, Shi-Wen,Peng, Yun-Gui
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experimental part
p. 921 - 928
(2012/06/17)
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- Modular amino acids and β-amino alcohol-based chiral ligands for enantioselective addition of diethylzinc to aromatic aldehydes
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Enantioselective addition of diethylzinc to a series of aromatic aldehydes was developed using a modular amino acids and ${bf beta}$-amino alcohol-based chiral ligand (2R)-N-[(1R,2S)-1-hydroxy-1-phenylpropan-2-yl]-3- phenyl-2-(tosylamino) propanamide (1f) without using titanium complex. The catalytic system employing 15 mol% of 1f was found to promote the addition of diethylzinc (ZnEt2) to a wide range of aromatic aldehydes with electron-donating and electron-withdrawing substituents, giving up to 97% ee of the corresponding secondary alcohol under mild conditions.
- Gou, Shaohua,Ye, Zhongbin,Gou, Guangjun,Feng, Mingming,Chang, Jing
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experimental part
p. 110 - 116
(2012/06/18)
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- Selective palladium-loaded MIL-101 catalysts
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Palladium nanoparticles (NPs) of different mean particle size have been synthesized in the host structure of the porous coordination polymer (or metal-organic framework: MOF) MIL-101. The metal-organic chemical vapor deposition method was used to load MIL-101 with the Pd precursor complex [(η5-C5H5)Pd(η3-C 3H5)]. Loadings higher than 50 wt.% could be accomplished. Reduction of the Pd precursor complex with H2 gave rise to Pd NPs inside the MIL-101 (Pd@MIL-101). The reduction conditions, especially the temperature, allows us to make size-conform (size of the Pd NPs correlates with the size of the cavities of the host structure of MIL-101) and undersized Pd NPs. The Pd@MIL-101 samples were characterized by X-ray diffraction, IR spectroscopy, Brauner-Emmett-Teller (BET) analysis, elemental analysis, and transmission electron microscopy (TEM). Catalytic studies, hydrogenation of ketones, were performed with selected Pd@MIL-101 catalysts. Activity, selectivity, and recyclability of the catalyst family are discussed.
- Hermannsdoerfer, Justus,Kempe, Rhett
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experimental part
p. 8071 - 8077
(2011/09/12)
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- Structurally constrained C1-1,1′-bisisoquinoline-based chiral ligands: geometrical implications on enantioinduction in the addition of diethylzinc to aldehydes
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New highly constrained chiral C1-1,1′-bisisoquinoline ligands have been synthesized. X-ray crystallographic analysis of these ligands showed peculiar structural differences between the parent 1′,2′,3′,4′-tetrahydro-1,1′-bisisoquinolin e and its alkyl, acyl and sulfonyl derivatives. The consequences of their geometrical conformations on enantioinduction were examined by employing the enantioselective addition of diethylzinc to aldehydes. Such conformations greatly affected the catalytic efficiency of these ligands.
- Qi, Gao,Judeh, Zaher M.A.
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experimental part
p. 429 - 436
(2010/07/02)
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- Enantioselective addition of diethylzinc to aryl aldehydes catalyzed by novel chiral imino alcohol ligands
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The enantioselective alkylation of aryl aldehydes by diethylzinc in the presence of catalytic amounts of several novel chiral imino alcohol ligands, synthesized from the reaction of (R)-2-amino-1-butanol with aromatic aldehydes, was studied. The influence of temperature and ligand structure was investigated and enantioselectivity up to 81% was obtained.
- Salehi,Dabiri,Kozehgary
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experimental part
p. 100 - 106
(2010/10/21)
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- Enantioselective addition of diethylzinc to aldehydes catalyzed by d-glucosamine derivatives: Highly pronounced effect of trifluoromethylsulfonamide
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We present the synthesis of β-hydroxy sulfonamides derived from d-glucosamine and their application as ligands in titanium tetraisopropoxide promoted enantioselective addition of diethylzinc to benzaldehyde and selected aromatic and aliphatic aldehydes. The N-trifluoromethylosulfonamido-d-glucosamine derivative is one of the most active ligands known and only 1 mol% of the ligand is sufficient for efficient catalysis of diethylzinc addition. The reaction is highly enantioselective for some aromatic aldehydes and enantiomeric excess up to 99% was obtained.
- Bauer, Tomasz,Smoliński, S?awomir
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experimental part
p. 247 - 251
(2010/11/18)
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- Synthesis and application of 3-substituted (S)-binol as chiral ligands for the asymmetric ethylation of aldehydes
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A series of (S)-BINOL ligands substituted at the 3 position with some five-membered nitrogen-containing aromatic heterocycles were effectively prepared and their catalytic abilities were evaluated in the asymmetric addition of diethylzinc to benzaldehyde in the presence of titanium tetraisopropoxide. Under the optimized reaction conditions, titanium complex of (S)-3-(1H-benzimidazol-1-yl)-1,1′-bi-2-naphthol was found to be the most efficient catalyst for asymmetric ethylation of various aldehydes to generate the corresponding secondary alcohols in up to 99% yield and 91% ee.
- Zhang, Zhi-Guang,Dong, Zhi-Bing,Li, Jin-Shan
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experimental part
p. 820 - 826
(2010/11/21)
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- Synthesis and structural features of chiral cyclic squaramides and their application in asymmetric catalytic reaction
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We report the synthesis and structural elucidation of two series of chiral cyclic squaramides, i.e. six-and twelve-membered ring squaramides 4 and 6, based on the cyclobutenedione structure, containing enantiomerically pure (1R,2R)-1,2-diphenylethylenediamine as the chiral element. Compounds 4a-d obtained from alkylation of 3, crystallize in space groups of monoclinic P2 1, monoclinic P21, monoclinic chiral P212 121, and the orthorhombic C2221, respectively. For the first time the crystal structures of six-membered ring chiral cyclic squaramides are reported. These novel ligands have been tested in the enantioselective addition of diethylzinc to aryl aldehydes to give the corresponding alcohols in moderate yields, albeit with low enantioselectivity. ARKAT-USA, Inc.
- Jin, Xiaoqing,Min, Qiaoqiao,Zheng, Yangfan,Wang, Pengcheng,Zhu, Jun,Zhou, Hai-Bing
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experimental part
p. 322 - 335
(2011/03/17)
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- Highly enantioselective addition of diethylzinc to aldehydes catalyzed by novel chiral tert-amino alcohols
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A series of novel chiral tert-amino alcohols 4a-h derived from enantiomerically pure phenylalanine were synthesized efficiently and used as chiral ligands in the catalytic enantioselective ethylation of aldehydes with diethylzinc (diethylzinc-to-aldehyde addition). The use of 10 mol % of the amino alcohols led to the corresponding sec-alcohols with excellent enantioselectivities (up to 100% ee) and high yields.
- Zhang, Cong-Hai,Yan, Sheng-Jiao,Pan, Sheng-Qiang,Huang, Rong,Lin, Jun
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experimental part
p. 869 - 873
(2010/10/04)
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- Alternative method for alkylation of arylpolyhalomethanes with trialkylborane in the presence of magnesium
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Reduction of benzal halide derivatives and α,α,α,-trichloromethylbenzene by magnesium powder in DMAc affords α-halocarbanions which then react with triethylborane to give alkylated products. After oxidation with H2O2-NaOH, secondary
- Condon, Sylvie,Nédélec, Jean-Yves
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supporting information; experimental part
p. 32 - 35
(2010/09/18)
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- N, N′-dioxide-Cu(OTf)2 complex catalyzed highly enantioselective amination reaction of N-acetyl enamide
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The N,N′-dioxide-Cu(OTf)2 complexes were applied in the asymmetric amination reaction of N-acetyl enamides with dialkyl azodicarboxylate, giving the corresponding products in good yields with high enantioselectivities (up to 91% ee). Precursors of vicinal diamine were readily obtained with excellent diastereoselectivities (>95:5) by NaBH4 reduction.
- Chang, Lu,Kuang, Yulong,Qin, Bo,Zhou, Xin,Liu, Xiaohua,Lin, Lili,Feng, Xiaoming
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supporting information; experimental part
p. 2214 - 2217
(2010/08/06)
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- 1, 4-butanediol as a reducing agent in transfer hydrogenation reactions
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1, 4-Butanediol is able to deliver two equivalents of H2 in hydrogen- transfer reactions to ketones, imines, and alkenes. Unlike simple alcohols, which establish equilibrium in the reduction of ketones, 1, 4-butanediol acts essentially irreversibly owing to the formation of butyrolactone, which acts as a thermodynamic sink. It is therefore not necessary to use 1, 4- butanediol in great excess in order to achieve reduction reactions. In addition, allylic alcohols are reduced to saturated alcohols through an isomerization/ reduction sequence using a ruthenium catalyst with 1, 4-butanediol as the reducing agent. Imines and alkenes are also reduced under similar conditions.
- Maytum, Hannah C.,Francos, Javier,Whatrup, David J.,Williams, Jonathan M. J.
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supporting information; experimental part
p. 538 - 542
(2010/08/06)
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- Screening of a modular sugar-based phosphoroamidite ligand library in the asymmetric nickel-catalyzed trialkylaluminium addition to aldehydes
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A modular sugar-based phosphoroamidite ligand library for the Ni-catalyzed trialkylaluminium addition to aldehydes has been synthesized and screened. After systematic variation of the sugar backbone, the substituents at the phosphoroamidite moieties and the flexibility of the ligand backbone, the monophosphoroamidite ligand 3-amine-3-deoxy-1,2:5,6-di-O-isopropylidene-((3,3′-di-trimethylsilyl-1,1′-biphenyl-2,2′-diyl)phosphite)-α-d-glucofuranose 1d were found to be optimal. Activities were high and enantioselectivities were good (ees up to 78%) for several aryl aldehydes.
- Raluy, Eva,Dieguez, Montserrat,Pamies, Oscar
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experimental part
p. 1575 - 1579
(2009/12/01)
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- Ruthenium-catalyzed redox isomerization/transfer hydrogenation in organic and aqueous media: A one-pot tandem process for the reduction of allylic alcohols
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The hexamethylbenzene-ruthenium(ii) dimer [{RuCl(μ-Cl) (η6-C6Me6)}2] 1 and the mononuclear bis(allyl)-ruthenium(iv) complex [RuCl2(η 3:η2:η3-C12H 18)]2, associated with base and a hydrogen donor, were found to be active catalysts for the selective reduction of the CC bond of allylic alcohols both in organic and aqueous media. The process, which proceeds in a one-pot manner, involves a sequence of two independent reactions: (i) the initial redox-isomerization of the allylic alcohol, and (ii) subsequent transfer hydrogenation of the resulting carbonyl compound. The highly efficient transformation reported herein represents, not only an illustrative example of auto-tandem catalysis, but also an appealing alternative to the classical transition-metal catalyzed CC hydrogenations of allylic alcohols. The process has been successfully applied to aromatic as well as aliphatic substrates affording the corresponding saturated alcohols in 45-100% yields after 1.5-24 h. The best performances were reached using (i) 1-5 mol% of 1 or 2, 2-10 mol% of Cs2CO3, and propan-2-ol or (ii) 1-5 mol% of 1 or 2, 10-15 equivalents of NaO2CH, and water. The catalytic efficiency is strongly related to the structure of the allylic alcohol employed. Thus, in propan-2-ol, the reaction rate essentially depends on the steric requirement around the CC bond, therefore decreasing with the increasing number of substituents. On other hand, in water the transformation is favoured for primary allylic alcohols vs. secondary ones.
- Cadierno, Victorio,Crochet, Pascale,Francos, Javier,Garcia-Garrido, Sergio E.,Gimeno, Jose,Nebra, Noel
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scheme or table
p. 1992 - 2000
(2010/06/19)
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