- Mild and stereoconvergent palladium-catalyzed carbonyl alkenation reaction of α,β-unsaturated aldehydes
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The addition of preformed ketone and ester enolates to α,β-unsaturated aldehydes 1 followed by in situ protection leads to the carbonates 3, 7, 8, 11, and 13. They are converted into sensitive functionalized dienes 4, 9, 12, and 14 by a smooth palladium-c
- Braun, Manfred,Mross, Stefan,Schwarz, Ido
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- Asymmetric dehydration of β-hydroxy esters via kinetic resolution
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Catalytic asymmetric dehydration of β-hydroxy esters via kinetic resolution has been investigated. The kinetic resolution of rac-β-hydroxy esters in the presence of prolinol chiral ligand 2a and BrZnCH2CO2t-Bu can provide highly enan
- Kim, Yongtae,Choi, Eui Ta,Lee, Min Hee,Park, Yong Sun
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Read Online
- Selective Construction of C?C and C=C Bonds by Manganese Catalyzed Coupling of Alcohols with Phosphorus Ylides
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Herein, we report the manganese catalyzed coupling of alcohols with phosphorus ylides. The selectivity in the coupling of primary alcohols with phosphorus ylides to form carbon-carbon single (C?C) and carbon-carbon double (C=C) bonds can be controlled by the ligands. In the conversion of more challenging secondary alcohols with phosphorus ylides the selectivity towards the formation of C?C vs. C=C bonds can be controlled by the reaction conditions, namely the amount of base. The scope and limitations of the coupling reactions were thoroughly evaluated by the conversion of 21 alcohols and 15 ylides. Notably, compared to existing methods, which are based on precious metal complexes as catalysts, the present catalytic system is based on earth abundant manganese catalysts. The reaction can also be performed in a sequential one-pot reaction generating the phosphorus ylide in situ followed manganese catalyzed C?C and C=C bond formation. Mechanistic studies suggest that the C?C bond was generated via a borrowing hydrogen pathway and the C=C bond formation followed an acceptorless dehydrogenative coupling pathway. (Figure presented.).
- Liu, Xin,Werner, Thomas
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supporting information
p. 1096 - 1104
(2020/12/31)
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- METHODS FOR PHOSPHINE OXIDE REDUCTION IN CATALYTIC WITTIG REACTIONS
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A method for increasing the rate of phosphine oxide reduction, preferably during a Wittig reaction comprising use of an acid additive is provided. A room temperature catalytic Wittig reaction (CWR) the rate of reduction of the phosphine oxide is increased due to the addition of the acid additive is described. Furthermore, the extension of the CWR to semi-stabilized and non-stabilized ylides has been accomplished by utilization of a masked base and/or ylide-tuning.
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Page/Page column 37; 43
(2014/09/29)
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- Palladium(ii)-catalyzed cross-coupling of simple alkenes with acrylates: A direct approach to 1,3-dienes through C-H activation
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The results from a direct palladium-catalyzed cross-coupling reaction between a variety of olefins with acrylate through vinylic C-H activation that give the corresponding butadienes in moderate to good yields and stereoselectivities are reported. Given the reaction's ability to tolerate a wide range of styrenes, aliphatic alkenes and acrylates, this atom- and step-economical methodology offers a straightforward method to forge new C-C bonds of the valuable diene products from readily available starting materials under very mild reaction conditions.
- Wen, Zhen-Kang,Xu, Yun-He,Loh, Teck-Peng
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p. 4520 - 4524
(2013/11/19)
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- Breaking the ring through a room temperature catalytic wittig reaction
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One ring no longer rules them all: Employment of 2.5-10 mol % of 4-nitrobenzoic acid with phenylsilane led to the development of a room temperature catalytic Wittig reaction (see scheme). Moreover, these enhanced reduction conditions also facilitated the use of acyclic phosphine oxides as catalysts for the first time. A series of alkenes were produced in moderate to high yield and selectivity. Copyright
- O'Brien, Christopher J.,Lavigne, Florie,Coyle, Emma E.,Holohan, Andrew J.,Doonan, Bryan J.
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supporting information
p. 5854 - 5858
(2013/06/27)
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- Pd(II)-catalyzed dehydrogenative olefination of vinylic C-H bonds with allylic esters: General and selective access to linear 1,3-butadienes
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This work demonstrates a general and efficient method to prepare conjugated dienes by Pd(II)-catalyzed direct olefination of unactivated alkenes with allylic esters and acrylates via vinylic C-H activation. Various aryl and heteroaryl alkenes as well as a
- Zhang, Yuexia,Cui, Zili,Li, Zejiang,Liu, Zhong-Quan
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supporting information; experimental part
p. 1838 - 1841
(2012/06/18)
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- Stereoselective olefination reactions promoted by Rieke manganese
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A study of the advantages of using manganese, an inexpensive and nontoxic metal, to perform stereoselective β-elimination reactions and to promote sequential olefination reactions of aldehydes to obtain α,β- unsaturated esters and amides is presented. Various elimination reactions, all of them characterized by occurring with complete stereoselectivity and in high yields, were performed using active manganese (Mn*) as metalating agent. This ability of manganese has been applied to develop a novel and direct synthesis of (E)-α,β-unsaturated esters or amides and (Z)-α,β-unsaturated α-halo esters and α-choroamides through a Mn*-mediated sequential olefination protocol of aldehydes with dichloro esters or amides and trihalo esters or trichloroamides, respectively. Georg Thieme Verlag Stuttgart.
- Concellon, Jose M.,Rodriguez-Solla, Humberto,Del Amo, Vicente,Diaz, Pamela
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experimental part
p. 2634 - 2645
(2009/12/06)
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- Asymmetric dehydration of β-hydroxy esters and application to the syntheses of flavane derivatives
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Catalytic asymmetric dehydration of β-aryl or alkyl substituted β-hydroxy esters via kinetic resolution has been investigated. A brief survey of 10 different chiral ligands is conducted to examine the effects of chiral ligand structure on selectivity of t
- Choi, Eui Ta,Lee, Min Hee,Kim, Yongtae,Park, Yong Sun
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p. 1515 - 1522
(2008/09/18)
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- Kinetic resolution of β-alkenyl-, β-alkynyl- and β-flavenyl-substituted β-hydroxy esters in asymmetric dehydration
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Catalytic asymmetric dehydration of β-alkenyl- or alkynyl-substituted β-hydroxy esters by kinetic resolution has been investigated with five different chiral ligands 3-7. The kinetic resolution of a variety of racemic β-hydroxy tert-butyl esters in the presence of a prolinol chiral ligand and BrZnCH2CO2tBu provided highly enantio-enriched β-hydroxy esters 9-22 with selectivity factors ranging from 11 to 59. In addition, the application of this asymmetric synthetic methodology to the preparation of enantio-enriched flavene derivatives 23-29 is demonstrated. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Min, Hee Lee,Eui, Ta Choi,Kim, Dajung,Yoon, Min Lee,Yong, Sun Park
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experimental part
p. 5630 - 5637
(2009/05/27)
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- Tandem olefin metathesis-elimination reactions. A new route to doubly unsaturated carbonyl derivatives
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Cross-metathesis between an activated olefin and an ethereal derivative of homoallylic alcohols leads to products that are subject to facile elimination resulting in α,β,γ,δ-unsaturated esters, ketones, acids, and aldehydes in high yields.
- Lipshutz, Bruce H.,Ghorai, Subir,Bo?kovi?, ?arko V.
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p. 6949 - 6954
(2008/09/20)
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- Oxidative palladium(II) catalysis: A highly efficient and chemoselective cross-coupling method for carbon-carbon bond formation under base-free and nitrogenous-ligand conditions
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We report herein the development of a general and mild protocol of oxygen-promoted Pd(II) catalysis resulting in the selective cross-couplings of alkenyl- and arylboron compounds with various olefins. Unlike most cross-coupling reactions, this new methodology works well even in the absence of bases, consequently averting undesired homo-couplings. Nitrogen-based ligands including dimethyl-phenanathroline enhance reactivities and offer a highly efficient and stereoselective methodology to overcome challenging substrate limitations. For instance, oxidative palladium(II) catalysis is effective with highly substituted alkenes and cyclic alkenes, which are known to be incompatible with other known catalytic conditions. Most examined reactions progressed smoothly to completion at low temperatures and in short times. These interesting results provide mechanistic insights and utilities for a new paradigm of palladium catalytic cycles without bases.
- Yoo, Kyung Soo,Yoon, Cheol Hwan,Jung, Kyung Woon
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p. 16384 - 16393
(2007/10/03)
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- The one-pot Wittig reaction: A facile synthesis of α,β- unsaturated esters and nitriles by using nanocrystalline magnesium oxide
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Nanocrystalline magnesium oxide was found to be an effective heterogeneous, solid base catalyst for the one-pot Wittig reaction to afford α,β-unsaturated esters and nitriles in excellent yields with high E-stereoselectivity in the presence of triphenylphosphine under mild conditions.
- Choudary, Boyapati M.,Mahendar, Koosam,Kantam, M. Lakshmi,Ranganath, Kalluri V. S.,Athar, Taimur
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p. 1977 - 1985
(2007/10/03)
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- Oxygen-promoted palladium(II) catalysis: Facile C(sp2)-C(sp 2) bond formation via cross-coupling of alkenylboronic compounds and olefins
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(Chemical Equation Presented) Oxygen-promoted Pd(II) catalysis facilitated the synthesis of conjugated dienes by cross-coupling of alkenylboronic compounds and various olefins including highly substituted alkenes and cyclohexenone. Under mild conditions, these versatile reactions were efficient and highly stereoselective.
- Cheol, Hwan Yoon,Kyung, Soo Yoo,Sung, Wook Yi,Mishra, Rajesh K.,Kyung, Woon Jung
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p. 4037 - 4039
(2007/10/03)
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- Oxidative heck-type reaction involving cleavage of a carbon-phosphorus bond of arylphosphonic acids
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Cleavage of a carbon-phosphorus bond is achieved under palladium catalysis in an oxidative Heck-type reaction which exploits arylphosphonic acids. The reaction of arylphosphonic acids with alkenes provides arylation products in good yields in the presence of TBAF with trimethylamine oxide as an oxidant. Copyright
- Inoue, Atsushi,Shinokubo, Hiroshi,Oshima, Koichiro
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p. 1484 - 1485
(2007/10/03)
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- Wittig-type olefination catalyzed by PEG-telluride
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Soluble poly(ethylene glycol) (PEG)-supported telluride 2 was designed and synthesized for catalytic Wittig-type reactions. It was found that the catalytic loading could be reduced from 20 to 2 mol % by the introduction of PEG (even to 0.5 mol % when some telluride salts were used as the catalyst). Under the catalytic reaction conditions, a wide variety of aldehydes with different structures could react with bromoacetate to afford β-substituted or α,β-disubstituted unsaturated esters in high yields with excellent E-stereoselectivity. The modified process, by using sodium bisulfite instead of triphenyl phosphite, represented a very simple product isolation procedure. The roles of PEG for promoting the ylide formation and stabilizing the catalytic species were disclosed. The mechanism was also studied.
- Huang, Zheng-Zheng,Ye, Song,Xia, Wei,Yu, Yi-Hua,Tang, Yong
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p. 3096 - 3103
(2007/10/03)
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- A practical catalytic Wittig-type reaction
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Soluble PEG-supported telluride 2 was synthesized and found to be an effective catalyst for the catalytic Wittig-type reaction to give a variety of α,β-unsaturated esters in high yields with excellent E-stereoselectivity in the presence of sodium bisulfite as well as triphenyl phosphite.
- Huang,Ye,Xia,Tang
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p. 1384 - 1385
(2007/10/03)
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- Reactions of t-butyl (trialkylstannyl)(trimethylgermyl)acetates and application of their anions to the Peterson-type reaction
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Three t-butyl (trialkylstannyl)(trimethylgermyl)acetates were synthesized and subjected to the Peterson-type reaction with carbonyl compounds. t-Butyl 2-(trimethylgermyl)-2-alkenoates were obtained as the main products from (tri-n-butyl-stannyl)-2-alkenoates and 2-alkenoates as minor products.
- Kanemoto, Naohide,Sato, Yoshiro,Inoue, Sumie
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