22751-68-4Relevant academic research and scientific papers
Development of Chiral Organosuperbase Catalysts Consisting of Two Different Organobase Functionalities
Kondoh, Azusa,Oishi, Masafumi,Terada, Masahiro,Tezuka, Hikaru
supporting information, p. 7472 - 7477 (2020/03/19)
In the field of chiral Br?nsted base catalysis, a new generation of chiral catalysts has been highly anticipated to overcome the intrinsic limitation of pronucleophiles that are applicable to the enantioselective reactions. Herein, we reveal conceptually new chiral Br?nsted base catalysts consisting of two different organobase functionalities, one of which functions as an organosuperbase and the other as the substrate recognition site. Their prominent activity, which stems from the distinctive cooperative function by the two organobases in a single catalyst molecule, was demonstrated in the unprecedented enantioselective direct Mannich-type reaction of α-phenylthioacetate as a less acidic pronucleophile. The present achievement would provide a new guiding principle for the design and development of chiral Br?nsted base catalysts and significantly broaden the utility of Br?nsted base catalysis in asymmetric organic synthesis.
Substrate-Induced Dimerization Assembly of Chiral Macrocycle Catalysts toward Cooperative Asymmetric Catalysis
Ao, Yu-Fei,Guo, Hao,Meng, Wei,Wang, De-Xian,Wang, Qi-Qiang,Zhang, Lie-Wei,Zhou, Hao
supporting information, p. 2623 - 2627 (2020/02/04)
An artificial system of substrate-induced dimerization assembly of chiral macrocycle catalysts enables a highly cooperative hydrogen-bonding activation network for efficient enantioselective transformation. These macrocycles contain two thiourea and two chiral diamine moieties and dimerize with sulfate to form a sandwich-like assembly. The macrocycles then adopt an extended conformation and reciprocally complement the hydrogen-bonding interaction sites. Inspired by the guest-induced dynamic assembly, these macrocycles catalyze the decarboxylative Mannich reaction of cyclic aldimines containing a sulfamate heading group. The imine substrate can be activated toward nucleophilic attack of β-ketoacid by a cooperative hydrogen-bonding network enabled by sulfamate-induced dimerization assembly of the macrocycle catalysts. Highly efficient (>95 % yield in most cases) and enantioselective (up to 97.5:2.5 er) transformation of a variety of substrates using only 5 mol % macrocycle was achieved.
Dynamic Kinetic Resolution of Heterobiaryl Ketones by Zinc-Catalyzed Asymmetric Hydrosilylation
Hornillos, Valentín,Carmona, José A.,Ros, Abel,Iglesias-Sigüenza, Javier,López-Serrano, Joaquín,Fernández, Rosario,Lassaletta, José M.
supporting information, p. 3777 - 3781 (2018/03/21)
A diastereo- and highly enantioselective dynamic kinetic resolution (DKR) of configurationally labile heterobiaryl ketones is described. The DKR proceeds by zinc-catalyzed hydrosilylation of the carbonyl group, thus leading to secondary alcohols bearing axial and central chirality. The strategy relies on the labilization of the stereogenic axis that takes place thanks to a Lewis acid–base interaction between a nitrogen atom in the heterocycle and the ketone carbonyl group. The synthetic utility of the methodology is demonstrated through stereospecific transformations into either N,N-ligands or appealing axially chiral, bifunctional thiourea organocatalysts.
Autocatalysis and surface catalysis in the reduction of imines by SmI 2
Rao, Chintada Nageswara,Hoz, Shmaryahu
experimental part, p. 14795 - 14803 (2011/10/31)
The reduction of the three imines, N-benzylidene aniline (BAI), N-benzylidenemethylamine (BMI), and benzophenone imine (BPI), with SmI 2 gives the reduced as well as coupled products. The reactions were found to be autocatalytic due to the formation of the trivalent samarium in the course of the reaction. When preprepared SmI3 was added to the reaction mixture, the reaction rate increased significantly. However, the kinetics were found to be of zero order in SmI2. This type of behavior is typical of surface catalysis with saturation of the catalytic sites. Although no solids are visible to the naked eye, the existence of microcrystals was proven by light microscopy as well as by dynamic light scattering analysis. Although HRTEM shows the existence of quantum dots in the solid, we were unable to make a direct connection between the existence of the quantum dots and the catalytic phenomenon. In the uncatalyzed reaction, the order of reactivity is BPI > BMI > BAI. This order does not conform to the electron affinity order of the substrates but rather to the nitrogen lone pair accessibility for complexation. This conclusion was further supported by using HMPA as a diagnostic probe for the existence of an inner sphere electron transfer reaction.
Indium trichloride: A versatile catalyst for the synthesis of fully saturated imidazoles
Kidwai, Mazaahir,Poddar, Priya Roona,Singhal, Kavita
experimental part, p. 886 - 892 (2009/12/24)
Ketimines are readily reduced to corresponding vicinal diamines using InCl3 and zinc followed by simple cyclization to fully saturated imidazoles with various aldehydes. InCl3 has been found to play an efficient catalytic role for th
Vanadium(I) chloride and lithium vanadium(I) dihydride as selective epimetallating reagents for π- and σ-bonded organic substrates
Eisch, John J.,Fregene, Paul O.
scheme or table, p. 4482 - 4492 (2009/05/07)
Subvalent vanadium(I) salts, of empirical formulas, VCl, vanadium(I) chloride and LiVH2, lithium vanadium(I) dihydride, whose efficient preparation, structural constitution and mode of reaction toward certain organic substrates have been described in a preceding article, are here evaluated in their reactions toward a wide variety of π- and σ-bonded organic substrates, namely carbonyl, imine, azo, alkene, 1,3-diene, nitrile π-bonds and C-X, C-O, C-N and N-N σ-bonds. Compared with the high reactivity of CrCl and LiCrH2 reagents in attacking both types of bonds, the VCl and LiVH2 reagents were much milder and selective in epimetallating π-bonds, often forming the 1:1 adduct of LiVH2 and π-bonded substrate as the major product. Finally, the vanadium reagents showed little tendency to cleave C-O, C-S and C-N bonds and a smaller scope in cleaving C-X bonds than their chromium counterparts. Because of their selectivity these vanadium reagents offer the following preparative promise: 1) smooth McMurry carbonyl coupling to their reductive dimers; 2) deoxygenation of epoxides; 3) selective aromatic C-X reduction; 4) high yields of epimetallated carbonyls or imines as intermediates to α-hydroxy and α-amino acids; 5) 1,4-reductions of 1,3-alkadienes; 6) reductive dimerization of nitriles to ketones; 7) 1,4 or 1,n-epimetallations leading to acyloins or indoles; and 8) reductive dimerizations of azines to produce unusual imidazole derivatives. In explaining the greater kinetic stability of the 1:1 LiVH2 adduct with carbonyl or imine substrates it is pointed out that such epimetallated adducts from LiVH2 would likely be diamagnetic, whereas such adducts from LiCrH2 have an unpaired electron on the Cr center and hence would rupture, so that the electron would be on the C center. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
Synthesis, resolution, and application of 2,2′-bis(diphenylphosphino) -3,3′-binaphtho[b]furan (BINAPFu)
Andersen, Nell G.,Parvez, Masood,McDonald, Robert,Keay, Brian A.
, p. 145 - 161 (2007/10/03)
(±)-2,2′-Bis(diphenylphosphino)-3,3′-binaphtho[2,1-b] furan (BINAPFu) was synthesized from 2-naphthoxyacetic acid in a five-step sequence in 62% overall yield. A variety of reported resolution procedures for biaryl bisphosphines did not work with (±)-BINAPFu; thus, a new resolution method was developed, involving the Staudinger reaction of the aforementioned racemate of BINAPFu with an enantiopure camphor sulfonyl azide derivative. The resulting diastereomeric phosphinimines were separated by flash chromatography. Subsequent hydrolysis to the corresponding bis-phosphine oxide and trichlorosilane reduction provided enantiopure BINAPFu. The absolute stereochemical configuration of BINAPFu was established by X-ray crystallography. BINAPFu was compared with commercially available 2,2′-bis(diphenylphosphino)-1,1′-binaphthalene (BINAP) in Pd(0)-catalyzed intermolecular Heck reactions. Investigation of the Heck arylation of 2,3-dihydrofuran showed BINAPFu to be more efficacious than BINAP in dioxane at 30°C. A variety of phosphorus selenides were prepared, and the 1JP-Se coupling constants measured, to obtain a comparative scale of parent phosphine basicity. The phosphorus atoms in BINAPFu were found to be electron deficient when compared with BINAP but slightly more electron rich than trifurylphosphine.
Iminopinacol coupling with lithium: Electron-transfer mediators
Mistryukov, Electron A.
, p. 230 - 231 (2007/10/03)
The addition of tert-butyl borate or ethyl formate to N-alkylbenzalimines directs the reaction pathway from the Birch reduction to the pinacol-type coupling with lithium in THF; an analogous reaction with a dimethylimmonium salt requires a trace titanium catalyst as the electron-transfer mediator.
An efficient method for the synthesis of N,N′-dimethyl-1,2-diamines
Tye, Heather,Eldred, Colin,Wills, Martin
, p. 155 - 158 (2007/10/03)
A simple method for the preparation of N,N′-dimethyl-1,2-diamines is described. The method requires the dimethylation of a diazaphospholidine oxide followed by acid-catalysed hydrolysis.
Reductive coupling of aromatic aldehydes and imines by the low valent titanium species generated in the reaction of TiCl4 with Et3N
Periasamy, Mariappan,Srinivas, Gadthula,Karunakar, Galla V.,Bharathi, Pandi
, p. 7577 - 7580 (2007/10/03)
Aromatic aldehydes and imines are converted to the corresponding diols and diamines using the low valent titanium species generated by the reaction of TiCl4 with triethylamine.
