39729-00-5Relevant academic research and scientific papers
Overcoming Scope Limitations in Cross-Coupling of Diazo Nucleophiles by Manipulating Catalyst Speciation and Using Flow Diazo Generation
Sullivan, Ryan J.,Freure, Garrett P.R.,Newman, Stephen G.
, p. 5623 - 5630 (2019/06/05)
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.
A 1,3,2-Diazaphospholene-Catalyzed Reductive Claisen Rearrangement
Reed, John H.,Donets, Pavel A.,Miaskiewicz, Solène,Cramer, Nicolai
supporting information, p. 8893 - 8897 (2019/05/28)
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.
Palladium-Catalyzed Reductive Coupling Reaction of Terminal Alkynes with Aryl Iodides Utilizing Hafnocene Difluoride as a Hafnium Hydride Precursor Leading to trans-Alkenes
Takahashi, Keita,Ogiwara, Yohei,Sakai, Norio
supporting information, p. 809 - 814 (2018/03/13)
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.
Ruthenium-Catalyzed C-H Allylation of Alkenes with Allyl Alcohols via C-H Bond Activation in Aqueous Solution
Wu, Xiaowei,Ji, Haitao
supporting information, p. 12094 - 12102 (2018/10/02)
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.
Switchable C-H Functionalization of N-Tosyl Acrylamides with Acryloylsilanes
Song, Shengjin,Lu, Ping,Liu, Huan,Cai, Sai-Hu,Feng, Chao,Loh, Teck-Peng
supporting information, p. 2869 - 2872 (2017/06/13)
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.
Rhodium-Catalyzed Hydrocarboxylation of Olefins with Carbon Dioxide
Kawashima, Shingo,Aikawa, Kohsuke,Mikami, Koichi
supporting information, p. 3166 - 3170 (2016/07/19)
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.
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
Shahid Islam,Ahmad, Syarhabil,Attu, Mary Rose,Foerstering, F. Holger,Mahmun Hossain
, p. 1273 - 1286 (2015/09/22)
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.
Rhodium(iii)-catalyzed C-H allylation of electron-deficient alkenes with allyl acetates
Feng, Chao,Feng, Daming,Loh, Teck-Peng
, p. 342 - 345 (2015/01/09)
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.
Rhodium(III)-catalyzed olefinic C-H alkynylation of acrylamides using tosyl-imide as directing group
Feng, Chao,Feng, Daming,Luo, Yang,Loh, Teck-Peng
, p. 5956 - 5959 (2015/01/08)
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.
Directing-group-assisted copper-catalyzed olefinic trifluoromethylation of electron-deficient alkenes
Feng, Chao,Loh, Teck-Peng
, p. 122414 - 122417 (2013/12/04)
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
