75677-02-0Relevant articles and documents
Transfer hydrogenations catalyzed by streptavidin-hosted secondary amine organocatalysts
Santi, Nicolò,Morrill, Louis C.,?widerek, Katarzyna,Moliner, Vicent,Luk, Louis Y. P.
supporting information, p. 1919 - 1922 (2021/03/02)
Here, the streptavidin-biotin technology was applied to enable organocatalytic transfer hydrogenation. By introducing a biotin-tethered pyrrolidine (1) to the tetrameric streptavidin (T-Sav), the resulting hybrid catalyst was able to mediate hydride transfer from dihydro-benzylnicotinamide (BNAH) to α,β-unsaturated aldehydes. Hydrogenation of cinnamaldehyde and some of its aryl-substituted analogues was found to be nearly quantitative. Kinetic measurements revealed that the T-Sav:1 assembly possesses enzyme-like behavior, whereas isotope effect analysis, performed by QM/MM simulations, illustrated that the step of hydride transfer is at least partially rate-limiting. These results have proven the concept thatT-Savcan be used to host secondary amine-catalyzed transfer hydrogenations.
Nickel-Catalyzed Decarboxylative Coupling of Redox-Active Esters with Aliphatic Aldehydes
Xiao, Jichao,Li, Zhenning,Montgomery, John
supporting information, p. 21234 - 21240 (2021/12/27)
The addition of alkyl fragments to aliphatic aldehydes is a highly desirable transformation for fragment couplings, yet existing methods come with operational challenges related to the basicity and instability of the nucleophilic reagents commonly employed. We report herein that nickel catalysis using a readily available bioxazoline (BiOx) ligand can catalyze the reductive coupling of redox-active esters with aliphatic aldehydes using zinc metal as the reducing agent to deliver silyl-protected secondary alcohols. This protocol is operationally simple, proceeds under mild conditions, and tolerates a variety of functional groups. Initial mechanistic studies suggest a radical chain pathway. Additionally, alkyl tosylates and epoxides are suitable alkyl precursors to this transformation providing a versatile suite of catalytic reactions for the functionalization of aliphatic aldehydes.
Radical Chain Reduction via Carbon Dioxide Radical Anion (CO2?-)
Hendy, Cecilia M.,Smith, Gavin C.,Xu, Zihao,Lian, Tianquan,Jui, Nathan T.
supporting information, p. 8987 - 8992 (2021/07/01)
We developed an effective method for reductive radical formation that utilizes the radical anion of carbon dioxide (CO2?-) as a powerful single electron reductant. Through a polarity matched hydrogen atom transfer (HAT) between an electrophilic radical and a formate salt, CO2?- formation occurs as a key element in a new radical chain reaction. Here, radical chain initiation can be performed through photochemical or thermal means, and we illustrate the ability of this approach to accomplish reductive activation of a range of substrate classes. Specifically, we employed this strategy in the intermolecular hydroarylation of unactivated alkenes with (hetero)aryl chlorides/bromides, radical deamination of arylammonium salts, aliphatic ketyl radical formation, and sulfonamide cleavage. We show that the reactivity of CO2?- with electron-poor olefins results in either single electron reduction or alkene hydrocarboxylation, where substrate reduction potentials can be utilized to predict reaction outcome.
Access to Trisubstituted Fluoroalkenes by Ruthenium-Catalyzed Cross-Metathesis
Nouaille, Augustin,Pannecoucke, Xavier,Poisson, Thomas,Couve-Bonnaire, Samuel
supporting information, p. 2140 - 2147 (2021/03/06)
Although the olefin metathesis reaction is a well-known and powerful strategy to get alkenes, this reaction remained highly challenging with fluororalkenes, especially the Cross-Metathesis (CM) process. Our thought was to find an easy accessible, convenient, reactive and post-functionalizable source of fluoroalkene, that we found as the methyl 2-fluoroacrylate. We reported herein the efficient ruthenium-catalyzed CM reaction of various terminal and internal alkenes with methyl 2-fluoroacrylate giving access, for the first time, to trisubstituted fluoroalkenes stereoselectively. Unprecedent TON for CM involving fluoroalkene, up to 175, have been obtained and the reaction proved to be tolerant and effective with a large range of olefin partners giving fair to high yields in metathesis products. (Figure presented.).
Synthesis of rac-ɑ-aryl propionaldehydes via branched-selective hydroformylation of terminal arylalkenes using water-soluble Rh-PNP catalyst
Chen, Fen-Er,Gao, Peng,Ke, Miaolin,Liang, Guanfeng,Ru, Tong
, (2021/08/26)
This work detailed the preparation of a class of water-soluble PNP ligands that differed by the nature of the substitute on phenyl ring of ligands. These ligands were incorporated into water-soluble rhodium-PNP complex catalysts that were used to regioselective hydroformylation of a series of terminal arylalkenes, providing efficient access to rac-α-aryl propionaldehydes in good to excellent yield (up to 97%) and branched-regioselectivity (up to 40:1 b/l ratio). Furthermore, gram-scale and diverse synthetic transformation demonstrated synthetic application of this methodology for non-steroidal antiinflammatory drugs.
Intermetallic Nanocatalyst for Highly Active Heterogeneous Hydroformylation
Chen, Minda,Gupta, Geet,Ordonez, Claudio W.,Lamkins, Andrew R.,Ward, Charles J.,Abolafia, Celia A.,Zhang, Biying,Roling, Luke T.,Huang, Wenyu
supporting information, p. 20907 - 20915 (2021/12/14)
Hydroformylation is an imperative chemical process traditionally catalyzed by homogeneous catalysts. Designing a heterogeneous catalyst with high activity and selectivity in hydroformylation is challenging but essential to allow the convenient separation and recycling of precious catalysts. Here, we report the development of an outstanding catalyst for efficient heterogeneous hydroformylation, RhZn intermetallic nanoparticles. In the hydroformylation of styrene, it shows three times higher turnover frequency (3090 h-1) compared to the benchmark homogeneous Wilkinson's catalyst (966 h-1), as well as a high chemoselectivity toward aldehyde products. RhZn is active for a variety of olefin substrates and can be recycled without a significant loss of activity. Density functional theory calculations show that the RhZn surfaces reduce the binding strength of reaction intermediates and have lower hydroformylation activation energy barriers compared to pure Rh(111), leading to more favorable reaction energetics on RhZn. The calculations also predict potential catalyst design strategies to achieve high regioselectivity.
Radical Carbonyl Propargylation by Dual Catalysis
Huang, Huan-Ming,Bellotti, Peter,Daniliuc, Constantin G.,Glorius, Frank
supporting information, p. 2464 - 2471 (2020/12/07)
Carbonyl propargylation has been established as a valuable tool in the realm of carbon–carbon bond forming reactions. The 1,3-enyne moiety has been recognized as an alternative pronucleophile in the above transformation through an ionic mechanism. Herein, we report for the first time, the radical carbonyl propargylation through dual chromium/photoredox catalysis. A library of valuable homopropargylic alcohols bearing all-carbon quaternary centers could be obtained by a catalytic radical three-component coupling of 1,3-enynes, aldehydes and suitable radical precursors (41 examples). This redox-neutral multi-component reaction occurs under very mild conditions and shows high functional group tolerance. Remarkably, bench-stable, non-toxic, and inexpensive CrCl3 could be employed as a chromium source. Preliminary mechanistic investigations suggest a radical-polar crossover mechanism, which offers a complementary and novel approach towards the preparation of valuable synthetic architectures from simple chemicals.
Insight into decomposition of formic acid to syngas required for Rh-catalyzed hydroformylation of olefins
Liu, Lei,Chen, Xiao-Chao,Yang, Shu-Qing,Yao, Yin-Qing,Lu, Yong,Liu, Ye
, p. 406 - 415 (2020/12/07)
Formic acid (FA) is one kind of important bulk chemicals, which is recognized as a sustainable and eco-friendly energy carrier to transport H2 via dehydrogenation or CO via decarbonylation. Expectantly, FA upon decomposition into H2 and CO could be used as the syngas alternative for hydroformylation. In this paper, the behaviors of FA to release H2 as well as CO following the distinct pathways were carefully investigated for the first time, and then established a new hydroformylation protocol free of syngas. It was found that the atmospheric hydroformylation of olefins with formic acid (FA) as syngas alternative was smoothly fulfilled over Xantphos (L1) modified Rh-catalyst under mild conditions (80 °C, Rh concentration 1 mol %, 14 h), resulting in >90% conversion of the olefins along with the high selectivity to the target aldehydes (>93%). By using FA as syngas source, the side-reaction of olefin-hydrogenation was greatly depressed. The in situ FT-IR and the high-pressure 1H NMR spectroscopic analyses were applied to reveal how FA behaves dually as CO surrogate and hydrogen source over L1-Rh(acac)(CO)2 catalytic system, based on which the deeply insight into the catalytic mechanism of hydroformylation of olefins with FA as syngas alternative was offered.
Multicatalytic approach to one-pot stereoselective synthesis of secondary benzylic alcohols
Casnati, Alessandra,Lichosyt, Dawid,Lainer, Bruno,Veth, Lukas,Dydio, Pawe?
supporting information, p. 3502 - 3506 (2021/05/10)
One-pot procedures bear the potential to rapidly build up molecular complexity without isolation and purification of consecutive intermediates. Here, we report multicatalytic protocols that convert alkenes, unsaturated aliphatic alcohols, and aryl boronic acids into secondary benzylic alcohols with high stereoselectivities (typically >95:5 er) under sequential catalysis that integrates alkene cross-metathesis, isomerization, and nucleophilic addition. Prochiral allylic alcohols can be converted to any stereoisomer of the product with high stereoselectivity (>98:2 er, >20:1 dr).
Chemo- And regioselective hydroformylation of alkenes with CO2/H2over a bifunctional catalyst
Hua, Kaimin,Liu, Xiaofang,Wei, Baiyin,Shao, Zilong,Deng, Yuchao,Zhong, Liangshu,Wang, Hui,Sun, Yuhan
supporting information, p. 8040 - 8046 (2021/11/01)
As is well known, CO2 is an attractive renewable C1 resource and H2 is a cheap and clean reductant. Combining CO2 and H2 to prepare building blocks for high-value-added products is an attractive yet challenging topic in green chemistry. A general and selective rhodium-catalyzed hydroformylation of alkenes using CO2/H2 as a syngas surrogate is described here. With this protocol, the desired aldehydes can be obtained in up to 97% yield with 93/7 regioselectivity under mild reaction conditions (25 bar and 80 °C). The key to success is the use of a bifunctional Rh/PTA catalyst (PTA: 1,3,5-triaza-7-phosphaadamantane), which facilitates both CO2 hydrogenation and hydroformylation. Notably, monodentate PTA exhibited better activity and regioselectivity than common bidentate ligands, which might be ascribed to its built-in basic site and tris-chelated mode. Mechanistic studies indicate that the transformation proceeds through cascade steps, involving free HCOOH production through CO2 hydrogenation, fast release of CO, and rhodium-catalyzed conventional hydroformylation. Moreover, the unconventional hydroformylation pathway, in which HCOOAc acts as a direct C1 source, has also been proved to be feasible with superior regioselectivity to that of the CO pathway.
