- Overcoming Scope Limitations in Cross-Coupling of Diazo Nucleophiles by Manipulating Catalyst Speciation and Using Flow Diazo Generation
-
The accessible scope of palladium-catalyzed diazo cross-coupling reactions has been expanded to include aryl chlorides by controlled diazo slow addition. The success of this strategy is based on manipulating speciation within the catalytic cycle through starvation of the diazo reagent to make the Pd(II) oxidative intermediate the resting state. The strategy is also applicable to cross-coupling reactions with aryl bromides and, in combination with safe, on-demand flow generation of nonstabilized diazo reagents, has been used to greatly expand the scope of applicable diazo compounds for this chemistry as well. Lastly, DFT calculations have provided insight into the mechanism and support for the proposed explanation for success of the slow addition strategy.
- Sullivan, Ryan J.,Freure, Garrett P.R.,Newman, Stephen G.
-
p. 5623 - 5630
(2019/06/05)
-
- A 1,3,2-Diazaphospholene-Catalyzed Reductive Claisen Rearrangement
-
1,3,2-Diazaphospholenes (DAPs) are an emerging class of organic hydrides. In this work, we exploited them as efficient catalysts for very mild reductive Claisen rearrangements. The method is tolerant towards a wide variety of functional groups and operates at ambient temperature. Besides being enantiospecific for substrates with existing stereogenic centers, the diastereoselectivity can be switched by varying solvents and DAP catalysts. The reaction kinetics show direct rearrangements of O-bound phospholene enolates and provide a proof-of-principle for catalytic enantioselective reactions.
- Reed, John H.,Donets, Pavel A.,Miaskiewicz, Solène,Cramer, Nicolai
-
supporting information
p. 8893 - 8897
(2019/05/28)
-
- Palladium-Catalyzed Reductive Coupling Reaction of Terminal Alkynes with Aryl Iodides Utilizing Hafnocene Difluoride as a Hafnium Hydride Precursor Leading to trans-Alkenes
-
Herein, we describe a reductive cross-coupling of alkynes and aryl iodides by using a novel catalytic system composed of a catalytic amount of palladium dichloride and a promoter precursor, hafnocene difluoride (Cp2HfF2, Cp=cyclopentadienyl anion), in the presence of a mild reducing reagent, a hydrosilane, leading to a one-pot preparation of trans-alkenes. In this process, a series of coupling reactions efficiently proceeds through the following three steps: (i) an initial formation of hafnocene hydride from hafnocene difluoride and the hydrosilane, (ii) a subsequent hydrohafnation toward alkynes, and (iii) a final transmetalation of the alkenyl hafnium species to a palladium complex. This reductive coupling could be chemoselectively applied to the preparation of trans-alkenes with various functional groups, such as an alkyl group, a halogen, an ester, a nitro group, a heterocycle, a boronic ester, and an internal alkyne.
- Takahashi, Keita,Ogiwara, Yohei,Sakai, Norio
-
supporting information
p. 809 - 814
(2018/03/13)
-
- Ruthenium-Catalyzed C-H Allylation of Alkenes with Allyl Alcohols via C-H Bond Activation in Aqueous Solution
-
A robust Ru(II)-catalyzed C-H allylation of electron-deficient alkenes with allyl alcohols in aqueous solution is reported. This method provides a straightforward and efficient access to the synthetically useful 1,4-diene skeletons. With the assistance of the N-methoxycarbamoyl directing group, this allylation reaction features a broad substrate scope with good functional group tolerance, excellent regio- and stereoselectivity, absence of metal oxidants, water-tolerant solvents, and mild reaction conditions. The mechanistic studies indicate that the process of the reversible C-H bond ruthenation is assisted by acetate, and the rate-determining step is unlikely to be the step of C-H bond cleavage.
- Wu, Xiaowei,Ji, Haitao
-
supporting information
p. 12094 - 12102
(2018/10/02)
-
- Switchable C-H Functionalization of N-Tosyl Acrylamides with Acryloylsilanes
-
A controllable Rh-catalyzed protocol to access alkylation and alkenylation-annulation of N-tosyl acrylamide with acryloyl silane is reported. In contrast to the directing group or catalyst-dependent divergent sp2 C-H alkylation/alkenylation, the intrinsic property of acryloylsilane allows the switchable reaction manifold, thereby affording either alkylation or annulation products with slight modification of the reaction conditions.
- Song, Shengjin,Lu, Ping,Liu, Huan,Cai, Sai-Hu,Feng, Chao,Loh, Teck-Peng
-
supporting information
p. 2869 - 2872
(2017/06/13)
-
- Rhodium-Catalyzed Hydrocarboxylation of Olefins with Carbon Dioxide
-
The catalytic hydrocarboxylation of styrenes derivatives and α,β-unsaturated carbonyl compounds with CO2(101.3 kPa) in the presence of an air-stable rhodium catalyst was explored. The combination of [RhCl(cod)]2(cod = cyclooctadiene) as a catalyst and diethylzinc as a hydride source allowed for effective hydrocarboxylation and provided the corresponding α-aryl carboxylic acids in moderate to excellent yields. In this catalytic process with carbon dioxide, intervention of the RhI–H species, which could be generated from the RhIcatalyst and diethylzinc, was clarified. Significantly, the catalytic asymmetric hydrocarboxylation of α,β-unsaturated esters with carbon dioxide was also performed by employing a cationic rhodium complex possessing (S)-(–)-4,4′-bi-1,3-benzodioxole-5,5′-diylbis(diphenylphosphine) [(S)-SEGPHOS] as a chiral diphosphine ligand. A plausible model for asymmetric induction was proposed by determination of the absolute configuration of the product.
- Kawashima, Shingo,Aikawa, Kohsuke,Mikami, Koichi
-
supporting information
p. 3166 - 3170
(2016/07/19)
-
- Concise Synthesis of 2-Arylpropanoic Acids and Study of Unprecedented Reduction of 3-Hydroxy-2-arylpropenoic Acid Ethyl Ester to 2-Arylpropenoic Acid Ethyl Ester by BH3·THF
-
We have developed a concise method of synthesizing racemic arylpropanoic acids, which have been widely used as nonsteroidal anti-inflammatory drugs (NSAIDs). The synthesis involves only four steps from commercially available benzaldehyde. The synthesis incorporates an unprecedented reduction reaction, conversion of 3-hydroxy-2-arylpropenoic acid ethyl ester to 2-arylpropenoic acid ethyl ester by BH3·THF. The reduction reaction has been investigated and optimized.
- Shahid Islam,Ahmad, Syarhabil,Attu, Mary Rose,Foerstering, F. Holger,Mahmun Hossain
-
p. 1273 - 1286
(2015/09/22)
-
- Rhodium(iii)-catalyzed C-H allylation of electron-deficient alkenes with allyl acetates
-
Rhodium-catalyzed C-H allylation of acrylamides with allyl acetates is reported. The use of weakly coordinating directing group resulted in high reaction efficiency, broad functionality tolerance and excellent γ-selectivity, which opens a new synthetic pathway for the access of 1,4-diene skeletons.
- Feng, Chao,Feng, Daming,Loh, Teck-Peng
-
p. 342 - 345
(2015/01/09)
-
- Rhodium(III)-catalyzed olefinic C-H alkynylation of acrylamides using tosyl-imide as directing group
-
The Rh(III)-catalyzed C-H alkynylation of acrylamide derivative is realized using a hypervalent alkynyl iodine reagent. The use of a weakly coordinating directing group proved to be of critical importance. This reaction displays broad functional group tolerance and high efficiency, which opens a new synthetic pathway to access functionalized 1,3-enyne skeletons.
- Feng, Chao,Feng, Daming,Luo, Yang,Loh, Teck-Peng
-
p. 5956 - 5959
(2015/01/08)
-
- Directing-group-assisted copper-catalyzed olefinic trifluoromethylation of electron-deficient alkenes
-
Assistance provided: The directing group in the title reaction not only activates the substrates but also allows the stereospecific formation of cis-trifluoromethylated products. The reaction is operationally simple and tolerates a wide variety of functional groups, thus providing an efficient method for the stereoselective synthesis of β-CF3-functionalized acrylamide derivatives. Copyright
- Feng, Chao,Loh, Teck-Peng
-
p. 122414 - 122417
(2013/12/04)
-
- Enantioselective enolate protonation in sulfamichael addition to r-substituted n-acryloyloxazolidin-2-ones with bifunctional organocatalyst
-
Organocatalytic conjugate addition of thiols to R-substituted N-acryloyloxazolidin-2-ones followed by asymmetric protonation has been studied in the presence of cinchona alkaloid derived thioureas. Both of the enantiomers are accessible with the same level of enantioselectivity using pseudoenantiomeric quinine/quinidine derived catalysts. The addition/protonation products have been converted to useful biologically active molecules. 2011 American Chemical Society.
- Rana, Nirmal K.,Singh, Vinod K.
-
supporting information; experimental part
p. 6520 - 6523
(2012/02/01)
-
- Synthesis of polysubstituted alkenes by Heck vinylation or Suzuki cross-coupling reactions in the presence of a tetraphosphane-palladium catalyst
-
Through the use of [PdCl(C3H5)]2/cis,cis,cis-1,2,3, 4-tetrakis[(diphenylphosphanyl)methyl]cyclopentane as a catalyst, a range of vinyl bromides undergo Suzuki cross-couplings with arylboronic acids in good yields. Furthermore, the catalyst can be used at low loadings, even for reactions of sterically hindered substrates. Mediated by this catalyst, stilbene and 1,1-diphenylethylene undergo Heck reactions with aryl halides to give triarylethylene derivatives. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.
- Berthiol, Florian,Doucet, Henri,Santelli, Maurice
-
p. 1091 - 1096
(2007/10/03)
-
- Facile synthesis of ethyl 2-arylpropenoates by cross-coupling reaction using electrogenerated highly reactive zinc
-
Highly reactive zinc metal was prepared by electrolysis of a DMF solution containing naphthalene and a supporting electrolyte in a one-compartment cell fitted with a platinum cathode and a zinc anode. This reactive zinc was used for efficient transformation of ethyl 2-bromoacrylate into the corresponding organozinc compound, which was reacted with various aryl iodides or bromides in the presence of 5 mol% Pd(P(o-Tol)3)2Cl2 to give the corresponding cross-coupling products in high yields. These cross-coupling reactions were successfully applied to a synthesis of the precursor of naproxen and cicloprofen, non-steroidal anti-inflammatory agent.
- Jalil, Aishah A,Kurono, Nobuhito,Tokuda, Masao
-
p. 7477 - 7484
(2007/10/03)
-
- Facile synthesis of 2-arylpropenoic acid esters by cross-coupling using electrogenerated highly reactive zinc and a palladium catalyst
-
Highly reactive zinc metal was prepared by electrolysis of a DMF solution containing naphthalene and a supporting electrolyte in a one-compartment cell fitted with a platinum cathode and a zinc anode. The reaction of this reactive zinc with ethyl 2-bromoacrylate at -20 °C and the following cross-coupling reaction with aryl iodides in the presence of 5 mol% Pd(P(o-Tol)3)2Cl2 at 70 °C gave the corresponding ethyl 2-arylpropenoates in almost quantitative yields.
- Jalil,Kurono,Tokuda
-
p. 1944 - 1946
(2007/10/03)
-
- How does organic structure determine organic reactivity? Nucleophilic substitution and alkene-forming elimination reactions of α-carbonyl and α-thiocarbonyl substituted benzyl derivatives
-
The effect of α-(N,N-dimethylcarbamoyl) and α-(N,N-dimethylthiocarbamoyl) substituents on the rate constants for partitioning of α-substituted 1-(4-methoxyphenyl)ethyl carbocations between nucleophilic addition of 50:50 (v:v) MeOH/H20 (k(s), s-1) and deprotonation by this solvent (k(e), s-1) have been investigated. The data show that these α-amide and α-thioamide substituents result in 80-fold and ≤ 30000-fold decreases, respectively, in k(s) for capture of the 4-methoxybenzyl carbocation by solvent, but that they lead to much smaller changes in k(e), for deprotonation of the corresponding α-substituted 1-(4-methoxyphenyl)ethyl carbocations by solvent. The large effect of the α-thioamide substituent on the partitioning of α-substituted 1-phenylethyl carbocations between formation of the products of solvolysis and elimination is therefore due primarily to the effect of this α-substituent on k(s), for capture of the carbocation by solvent. The results of experimental and computational studies are consistent with the conclusion that the relative magnitude of the rate constants k(s) and k(e) for partitioning of α-substituted 1-phenylethyl carbocations is strongly controlled by the relative thermodynamic stabilities of the neutral products of these reactions.
- Richard, John P.,Lin, Shrong-Shi,Buccigross, Jeanne M.,Amyes, Tina L.
-
p. 12603 - 12613
(2007/10/03)
-
- Intramolecular Carbenoid Reactions of Pyrrole Derivatives. A Total Synthesis of (+/-)-Ipalbidine
-
A mew method for alkaloid synthesis is described.The rhodium(II)-acetate-catalyzed decomposition of 3-(4-acetoxyphenyl)-1-diazo-4-(pyrrol-1-yl)-2-butanone (5d) gave 6-(4-acetoxyphenyl)-5,6-dihydro-7(8H)-indolizinone (6d) in 82percent yield via an intramolecular carbenoid reaction.The latter compound was converted in four steps in 13percent overall yield to (+/-)-ipalbidine (1b).
- Jefford, Charles W.,Kubota, Tadatoshi,Zaslona, Alexander
-
p. 2048 - 2061
(2007/10/02)
-
- COMPETITIVE INTRAMOLECULAR CARBENOID REACTIONS OF PYRROLE DERIVATIVES
-
Rhodium(II) acetate-catalyzed decomposition of 1-diazo-3-phenyl-4-(pyrrol-1-yl)-butan-2-one and its p-methoxy derivative resulted in their intramolecular cyclization to form the 6-phenyl-5,6-dihydroindolizin-7(8H)-ones and 1-(pyrrol-1-yl)methylindan-3-ones as major and minor products respectively in high yields (77-89percent).The p-nitrophenyldiazo compound cyclized exclusively to the 5,6-dihydroindolizin-7(8H)-one in 76percent yield.
- Jefford, Charles W.,Zaslona, Alexander
-
p. 6035 - 6038
(2007/10/02)
-