61866-20-4Relevant academic research and scientific papers
Siloxy Esters as Traceless Activators of Carboxylic Acids: Boron-Catalyzed Chemoselective Asymmetric Aldol Reaction**
Fujita, Taiki,Kanai, Motomu,Mitsunuma, Harunobu,Sameera, W. M. C.,Yamane, Mina
supporting information, p. 24598 - 24604 (2021/10/14)
The catalytic asymmetric aldol reaction is among the most useful reactions in organic synthesis. Despite the existence of many prominent reports, however, the late-stage, chemoselective, catalytic, asymmetric aldol reaction of multifunctional substrates is still difficult to achieve. Herein, we identified that in situ pre-conversion of carboxylic acids to siloxy esters facilitated the boron-catalyzed direct aldol reaction, leading to the development of carboxylic acid-selective, catalytic, asymmetric aldol reaction applicable to multifunctional substrates. Combining experimental and computational studies rationalized the reaction mechanism and led to the proposal of Si/B enediolates as the active species. The silyl ester formation facilitated both enolization and catalyst turnover by acidifying the α-proton of substrates and attenuating poisonous Lewis bases to the boron catalyst.
Chain propagation determines the chemo- And regioselectivity of alkyl radical additions to C-O: Vs. C-C double bonds
Paulisch, Tiffany O.,Strieth-Kalthoff, Felix,Henkel, Christian,Pitzer, Lena,Guldi, Dirk M.,Glorius, Frank
, p. 731 - 736 (2020/02/03)
Investigations into the selectivity of intermolecular alkyl radical additions to C-O- vs. C-C-double bonds in α,β-unsaturated carbonyl compounds are described. Therefore, a photoredox-initiated radical chain reaction is explored, where the activation of the carbonyl-group through an in situ generated Lewis acid-originating from the substrate-enables the formation of either C-O or the C-C-addition products. α,β-Unsaturated aldehydes form selectively 1,2-, while esters and ketones form the corresponding 1,4-addition products exclusively. Computational studies lead to reason that this chemo- and regioselectivity is determined by the consecutive step, i.e. an electron transfer, after reversible radical addition, which eventually propagates the radical chain.
Copper-catalyzed diastereoselective synthesis of β-boryl-α-quaternary carbon carboxylic esters
Zuo, Ya-Jie,Zhong, Zhuoran,Fan, Yinkun,Li, Xiangyu,Chen, Xiaolu,Chang, Yuwei,Song, Ruihu,Fu, Xinpeng,Zhang, Anling,Zhong, Chong-Min
supporting information, p. 9237 - 9242 (2019/01/03)
Cu(i)-Catalyzed diastereoselective carboboration of α-alkyl-substituted α,β-unsaturated carboxylic esters to produce β-boryl-α-quaternary carbon esters was developed. The carbon skeletons of dialkyl sulfates, primary allyl halides, and benzyl bromides were transferred to the α-position of the substrates to provide products in moderate to good yields with a diastereoselectivity of >95% in most cases. Substrates bearing a β-(hetero)aryl substituent gave higher diastereoselectivities than those bearing a linear β-alkyl substituent. The crystal structure of the potassium trifluoroborate derivative shows that the reactions probably go through a copper(i) enolate intermediate and the diastereoselectivity arises from the electrophilic attack of electrophiles to the less hindered side of the enolates.
Strong Lewis acid air-stable cationic titanocene perfluoroalkyl(aryl) sulfonate complexes as highly efficient and recyclable catalysts for C-C bond forming reactions
Li, Ningbo,Wang, Jinying,Zhang, Xiaohong,Qiu, Renhua,Wang, Xie,Chen, Jinyang,Yin, Shuang-Feng,Xu, Xinhua
supporting information, p. 11696 - 11708 (2014/07/22)
A series of strong Lewis acid air-stable titanocene perfluoroalkyl(aryl) sulfonate complexes Cp2Ti(OH2)2(OSO 2X)2·THF (X = C8F17, 1·THF; X = C4F9, 2·H2O· THF; X = C6F5, 3) were successfully synthesized by the treatment of Cp2TiCl2 with C8F 17SO3Ag, C4F9SO3Ag and C6F5SO3Ag, respectively. In contrast to well-known titanocene bis(triflate), these complexes showed no change in open air over three months. TG-DSC analysis showed that 1·THF, 2·H 2O·THF and 3 were thermally stable at 230 °C, 220°C and 280°C, respectively. Conductivity measurements showed that these complexes underwent ionic dissociation in CH3CN solution. X-ray analysis results confirmed that 2·H2O·THF and 3 were cationic. ESR spectra showed that the Lewis acidity of 1·THF (1.06 eV) was higher than that of Sc3+ (1.00 eV) and Y3+ (0.85 eV). UV/Vis spectra showed a significant red shift due to the strong complex formation between 10-methylacridone and 2·H2O·THF. Fluorescence spectra showed that the Lewis acidity of 2 (λem = 477 nm) was higher than that of Sc3+ (λem = 474 nm). These complexes showed high catalytic ability in various carbon-carbon bond forming reactions. Moreover, they show good reusability. Compared with 1·THF, 2·H2O·THF and 3 exhibit higher solubility and better catalytic activity, and will find broad applications in organic synthesis. This journal is the Partner Organisations 2014.
Mukaiyama aldol reactions catalyzed by a trimeric organo aluminum(III) alkoxide
Kim, So Han,Yoon, Sungwoo,Kim, Youngjo,Verkade, John G.
, p. 1193 - 1206 (2014/09/30)
Mukaiyama aldol reactions of enol ethers with a variety of aldehydes and ketones are efficiently catalyzed at 0-25 °C by the sterically bulky trimeric organo aluminum(III) alkoxide 1 synthesized via the reaction of 3 equiv of AlMe3 with tripodal tris(2-hydroxy-3-tert-butyl-5-methylphenyl) methane and the elimination of 3 equiv of methane. Comparisons of its catalytic properties with the less sterically hindered analogue 2, the more sterically hindered analogue 3, a monomeric aluminum near-analogue 4, and a dimeric alumatrane 5 revealed that 1 possesses superior activity.
Synthesis and structures of air-stable binuclear hafnocene perfluorobutanesulfonate and perfluorobenzenesulfonate and their catalytic application in C-C bond-forming reactions
Li, Ningbo,Zhang, Xiaohong,Xu, Xinhua,Chen, Yun,Qiu, Renhua,Chen, Jinyang,Wang, Xie,Yin, Shuang-Feng
supporting information, p. 2430 - 2440 (2013/10/01)
The two air-stable m2-hydroxy-bridged binuclear hafnocene perfluorobutanesulfonate and perfluorobenzenesulfonate complexes were successfully synthesized. The high catalytic activity and recyclability of these complexes were exemplified for various carbon-carbon bond formation reactions. Compared with our previously reported hafnocene perfluorooctanesulfonate, these complexes show stronger Lewis acidity and better catalytic activity, and should find broad applications in organic synthesis.
Mukaiyama aldol reaction of trimethylsilyl enolate with aldehyde catalyzed by CuI
Kalita, Hima Rani,Borah, Arun Jyoti,Phukan, Prodeep
, p. 289 - 292 (2013/05/22)
Cuprous iodide has been found to be a very effective catalyst for Mukaiyama aldol reaction of trimethylsilyl ketene acetal with aldehydes. The new catalytic system promotes efficiently the Mukaiyama aldol reaction in DMF to produce corresponding β-hydroxy carbonyl compounds in high yield.
Gallium(III) triflate catalyzed diastereoselective mukaiyama aldol reaction by using low catalyst loadings
Plancq, Baptiste,Justafort, Lyse Carole,Lafantaisie, Mathieu,Ollevier, Thierry
supporting information, p. 6525 - 6529 (2013/11/06)
A mild method for the diastereoselective Mukaiyama aldol reaction is reported. By using a low loading of the gallium(III) triflate catalyst (down to 0.01 mol-%), the transformation proceeds efficiently to afford the corresponding β-hydroxy ketones in yields up to 92a€‰%. To the best of our knowledge, this is the first report of a metal triflate acting as a safe, bench-stable, and slow-releasing source of triflic acid for the Mukaiyama aldol reaction. A diastereoselective Mukaiyama aldol reaction was performed under mild conditions with a low loading of the gallium(III) triflate catalyst (down to 0.01 mol-%). The transformation proceeded efficiently to afford the corresponding β-hydroxy ketones in yields up to 92a€‰%. Copyright
Strong Lewis acids of air-stable metallocene bis(perfluorooctanesulfonate)s as high-efficiency catalysts for carbonyl-group transformation reactions
Qiu, Renhua,Xu, Xinhua,Peng, Lifeng,Zhao, Yalei,Li, Ningbo,Yin, Shuangfeng
supporting information; experimental part, p. 6172 - 6182 (2012/06/30)
Strong Lewis acids of air-stable metallocene bis(perfluorooctanesulfonate)s [M(Cp)2][OSO2C8F17] 2·nH2O·THF (M=Zr (2 a·3 H 2O·THF), M=Ti (2 b·2 H2O·THF)) were synthesized by the reaction of [M(Cp)2]Cl2 (M=Zr (1 a), M=Ti (1 b)) with nBuLi and C8F17SO3H (2 equiv) or with C8F17SO3Ag (2 equiv). The hydrate numbers (n) of these complexes were variable, changing from 0 to 4 depending on conditions. In contrast to well-known metallocene triflates, these complexes suffered no change in open air for a year. thermogravimetry-differential scanning calorimetry (TG-DSC) analysis showed that 2 a and 2 b were thermally stable at 300 and 180 °C, respectively. These complexes exhibited unusually high solubility in polar organic solvents. Conductivity measurement showed that the complexes (2 a and 2 b) were ionic dissociation in CH3CN solution. X-ray analysis result confirmed 2 a·3 H2O·THF was a cationic organometallic Lewis acid. UV/Vis spectra showed a significant red shift due to the strong complex formation between 10-methylacridone and 2 a. Fluorescence spectra showed that the Lewis acidity of 2 a fell between those of Sc3+ (λem=474 nm) and Fe3+ (λem=478 nm). ESR spectra showed the Lewis acidity of 2 a (0.91 eV) was at the same level as that of Sc3+ (1.00 eV) and Y 3+ (0.85 eV), while the Lewis acidity of 2 b (1.06 eV) was larger than that of Sc3+ (1.00 eV) and Y3+ (0.85 eV). They showed high catalytic ability in carbonyl-compound transformation reactions, such as the Mannich reaction, the Mukaiyama aldol reaction, allylation of aldehydes, the Friedel-Crafts acylation of alkyl aromatic ethers, and cyclotrimerization of ketones. Moreover, the complexes possessed good reusability. On account of their excellent catalytic efficiency, stability, and reusability, the complexes will find broad catalytic applications in organic synthesis. Copyright
