20261-65-8Relevant articles and documents
Axially Chiral Bifunctional 8,8′-Biquinolyl: Synthesis of 7,7′-Dihydroxymethyl-8,8′-biquinolyl via Pd-Catalyzed Double C-H Oxidation of 7,7′-Dimethyl-8,8′-biquinolyl
Kitamura, Mitsuru,Fukuma, Hiroaki,Kobayashi, Mitsuaki,Okayama, Shinya,Okauchi, Tatsuo
, p. 3956 - 3960 (2016)
Bifunctional C2-symmetric 7,7′-dihydroxymethyl-8,8′-biquinolyl (2) was synthesized in short steps via (i) Cu/Pd-catalyzed homo coupling of 7-methyl-8-bromoquinoline and (ii) Pd(II)-catalyzed double C-H oxidation. Axial chirality of 2 and its synthetic precursor 7,7′-dimethyl-8,8′-biquinolyl (3) is stable. Optically active 2 was obtained through separation of racemic 2 by chiral column HPLC or Pd(II)-catalyzed double C-H oxidation of optically active 3. The absolute stereochemistry of enantiomers of 2 and 3 was determined using the exciton chirality method.
New 2,2′-substituted 6,6′-dimethylbiphenyl derivatives inducing strong helical twisting power in liquid crystals
Holzwarth, Richard,Bartsch, Richard,Cherkaoui, Zoubair,Solladie, Guy
, p. 3536 - 3541 (2005)
New optically active tetra-ortho-substituted biphenyl chiral dopants for nematic liquid crystals are described. It was shown, with respect to our previous results, that biphenyl chiral dopants bearing only mesogenic residues on their 2,2′-positions and wi
Method for resolving chiral compound
-
, (2020/08/27)
The invention relates to the field of organic chemistry, in particular to a method for resolving a chiral compound. The method for splitting the chiral compound provided by the invention comprises thestep of carrying out addition reaction on a racemic compound shown as a formula A and azodicarbonic acid ester in the presence of a catalyst so as to provide an S-configuration compound shown as theformula A and an S-configuration compound shown as the formula C. According to the method, chiral phosphoric acid is used as a catalyst; good catalytic effect is achieved, and very wide substrate applicability is also achieved; the product and the recovered raw material can be obtained with excellent enantioselectivity, the selectivity coefficient of kinetic resolution can reach 371, and the method has an excellent kinetic resolution effect on various N-monosubstituted and N-unsubstituted binaphthalene diamines, H8-binaphthalene diamines and biphenyl diamines.
A Versatile Method for Kinetic Resolution of Protecting-Group-Free BINAMs and NOBINs through Chiral Phosphoric Acid Catalyzed Triazane Formation
Jiang, Qianwen,Liu, Wei,Yang, Xiaoyu
, p. 23598 - 23602 (2020/10/23)
A versatile kinetic resolution of protecting-group-free BINAMs and NOBINs has been realized through chiral phosphoric acid catalyzed triazane formation with azodicarboxylates. A series of mono-N-protected and unprotected BINAMs, diphenyl diamines and NOBIN derivatives could be kinetically resolved with excellent performances (with s factor up to 420). The gram-scale reactions and facile derivatizations of the chiral products demonstrate the potential of these methods in the asymmetric synthesis of chiral catalysts and ligands.
Biphenyl-Based Bis(thiourea) Organocatalyst for Asymmetric and syn -Selective Henry Reaction
Otevrel, Jan,Bobal, Pavel
supporting information, p. 593 - 603 (2017/01/25)
A scalable, efficient and chromatography-free synthesis of a new enantiopure C 2-symmetric bis(thiourea) catalyst was accomplished from a readily available starting material. The developed strategy could be conducted on a multi-gram scale. Both the prepared enantiomers of the bis(thiourea) organocatalyst have been tested in the asymmetric Henry reaction under thoroughly optimized conditions during which an unusual solvent effect on enantioselectivity was found. The corresponding adducts were obtained in excellent yields with good to excellent enantioselectivities. The achieved high reactivity and enantioselectivity in the nitroaldol reaction of nitroalkanes with aromatic aldehydes suggests promising potential for this catalyst. Moreover, a significant syn-diastereoselectivity was observed.
Catalytic, Enantioselective Sulfenylation of Ketone-Derived Enoxysilanes
Denmark, Scott E.,Rossi, Sergio,Webster, Matthew P.,Wang, Hao
, p. 13016 - 13028 (2015/09/15)
A catalytic, enantioselective, Lewis base-catalyzed α-sulfenylation of silyl enol ethers has been developed. To avoid acidic hydrolysis of the silyl enol ether substrates, a sulfenylating agent that did not require additional Br?nsted acid activation, namely N-phenylthiosaccharin, was developed. Three classes of Lewis bases - tertiary amines, sulfides, and selenophosphoramides - were identified as active catalysts for the α-sulfenylation reaction. Among a wide variety of chiral Lewis bases in all three classes, only chiral selenophosphoramides afforded α-phenylthio ketones in generally high yield and with good enantioselectivity. The selectivity of the reaction does not depend on the size of the silyl group but is highly sensitive to the double bond geometry and the bulk of the substituents on the double bond. The most selective substrates are those containing a geminal bulky substituent on the enoxysilane. Computational analysis revealed that the enantioselectivity arises from an intriguing interplay among sterically guided approach, distortion energy, and orbital interactions.
Bidentate chelating N-heterocyclic carbene complexes of palladium: Synthesis and structure
Nan, Guangming,Qin, Yuancheng,Wei, Zhijun
experimental part, p. 285 - 290 (2012/06/01)
The new cyclometalated racemic-chelated N-heterocyclic carbene palladium (II) complexes Fa-b derived from G have been prepared. The structure of cyclometalated race-chelated bidentate NHC-palladium (II) complexes F a-b was characteri
Chiral neutral zirconium amidate complexes for the asymmetric hydroamination of alkenes
Wood, Mark C.,Leitch, David C.,Yeung, Charles S.,Kozak, Jennifer A.,Schafer, Laurel L.
, p. 354 - 358 (2007/10/03)
Aminations with amidates: The first C2-symmetric amidate complexes of zirconium were used for catalytic asymmetric hydroaminations of amino alkenes to prepare chiral gem-disubstituted pyrrolidines with up to 93 % ee (see scheme). The modular nature of the chiral complexes facilitates their preparation and screening as catalysts. (Chemical Equation Presented).
Enantioselective aziridination using copper complexes of biaryl Schiff bases
Gillespie, Kevin M.,Sanders, Christopher J.,O'Shaughnessy, Paul,Westmoreland, Ian,Thickitt, Christopher P.,Scott, Peter
, p. 3450 - 3458 (2007/10/03)
Racemic 2,2′-diamino-6,6′-dimethylbiphenyl is resolved using simulated moving bed chromatography, and the absolute configuration of the enantiomers is confirmed via the X-ray crystal structure of a derivative. The diamine is condensed with a range of aldehydes to give bidentate aldimine proligands L. Molecular structures of the complexes formed between L and Cu(I) fall into two classes; bimetallic double helices ([Cu2L2]2+) and monometallic ([CuL]+). The latter are strikingly more efficient in the aziridination of alkenes than are the former in terms of rate, turnover, and enantioselection. In particular, the imine ligand formed from the diamine and 2,6-dichlorobenzaldehyde gives, in combination with Cu(I) or Cu(II), up to 99% ee in the aziridination of 6-acyl-2,2-dimethylchromene and 88-98% ee for a range of cinnamate esters. Styrenic and other alkenes are converted with lower selectivities (5-54%). The catalytic system shows a linear response in product ee to catalyst ee, and the product ee does not vary significantly during the reaction. UV spectrophotometric investigations indicate that conversion of Cu(I) to Cu(II) is not essential for catalysis but that Cu(II) is probably also a competent system.
An efficient access to (R)- and (S)-6,6'-dimethoxy-2,2'-diiodo-1,1'-biphenyl
Cereghetti, Marco,Schmid, Rudolf,Schoenholzer, Peter,Rageot, Alain
, p. 5343 - 5346 (2007/10/03)
In a better procedure than the known for (rac)-2a, the diamine (rac)-2b was resolved for the first time with the new resolving agent (R,R)- and (S,S)-2,3-di(phenylaminocarbonyl)tartaric acid (5c) (40-45% weight yields; >99% ee). The diamines (R)- and (S)-2a and 2b were converted with >98% stereochemical retention into the diiodides (R)- and (S)-3a and 3b and subsequently, without loss of optical purity, diphenylphosphinated to the known diphosphines (R)- and (S)-4a and 4b.
