220091-30-5Relevant academic research and scientific papers
Novel tetradentate bisoxazoline ligands from l-serine and β-DDB for asymmetric pinacol coupling reactions of aromatic aldehydes
Wen, Jiwu,Liu, Limin,Zhou, Xiaochun,Hu, Ronghua,Xu, Yaping
, p. 860 - 865 (2013/08/23)
A variety of novel hydroxyl-containing tetradentate bisoxazolines were successfully synthesized from natural l-serine and β-DDB. The applications of these ligands in the asymmetric pinacol coupling of aromatic aldehydes revealed that the absolute configurations of the resulting pinacols were entirely dominated by the axial chirality of the biphenyl component and that the bulky substituent adjacent to the hydroxyl group was favorable for achieving both high diastereoselectivities and enantioselectivities. Among the ligands screened, (S,aR,S)-1c exhibited much better asymmetric induction capacity to furnish the (R,R)-pinacols with diastereoselectivities up to 99/1 and with 63-89% enantiomeric excess. A plausible mechanism of the asymmetric pinacol coupling was also suggested.
Enantioselective pinacol coupling reaction of aromatic aldehydes catalyzed by chiral vanadium complexes
Sun, Jiangtao,Dai, Zhenya,Li, Changsi,Pan, Xu,Zhu, Chengjian
experimental part, p. 3219 - 3221 (2010/01/11)
The asymmetric pinacol coupling of aromatic aldehydes by chiral salan-vanadium complexes as effective catalysts is reported. Chiral 1,2-diols were obtained with high diastereoselectivities (up to 90/10) and moderate to high enantioselectivities (up to 82%
Truly catalytic and enantioselective pinacol coupling of aryl aldehydes mediated by chiral Ti(III) complexes
Chatterjee,Bennur,Joshi
, p. 5668 - 5671 (2007/10/03)
A variety of chiral Ti(IV) complexes were reduced in situ with zinc in acetonitrile. The resulting chiral Ti(III) complexes were found to catalyze the pinacol coupling reaction stereoselectively. The best results were obtained from the Ti-SALEN complex, which was found to be an efficient catalyst at 10 mol % concentration. Various aromatic aldehydes were coupled to obtain chiral hydrobenzoin derivatives with high diastereoselectivity and enantioselectivity. A plausible mechanism is proposed that rationalizes the stereochemical outcome of the reaction.
A practical stereoselective synthesis of chiral hydrobenzoins via asymmetric transfer hydrogenation of benzils
Murata, Kunihiko,Okano, Kazuya,Miyagi, Miwa,Iwane, Hiroshi,Noyori, Ryoji,Ikariya, Takao
, p. 1119 - 1121 (2008/02/09)
(matrix presented) Asymmetric reduction of benzil with RuCl[(S,S)-Tsdpen)(η6-p-cymene) in a mixture of formic acid and triethylamine proceeds with a substrate/ catalyst molar ratio of 1000-2000 to give (R,R)-hydrobenzoin quantitatively with high diastereomeric (97% de) and enantiomeric purities (>99% ee), in which the benzoin intermediate with a chirally labile stereogenic center is converted to one major stereoisomer, (R,R)-product, via dynamic kinetic resolution.
A comparative study of C2-symmetric bis(aziridine) ligands in some transition metal-mediated asymmetric transformations
Tanner, David,Johansson, Fredrik,Harden, Adrian,Andersson, Pher G.
, p. 15731 - 15738 (2007/10/03)
A comparative study has been made of the performance of differently substituted C2-symmetric bis(aziridine) ligands in a variety of metal- mediated asymmetric reactions. The metals studied were osmium (dihydroxylation), palladium (allylic alkylation) and copper (cyclopropanation and aziridination), the ligands being chosen so as to allow evaluation of both electronic and steric effects. The electronic effects were most pronounced for complexes of palladium, which seem to bind rather loosely to this type of ligand. For the other metals, steric effects play a more important role.
