Determination of the enantiomeric excesses of chiral acids by 19F NMR studies of their esters deriving from (R)-(+)-2-(trifluoromethyl)benzhydrol
摘要:
15 Chiral acids were esterified with optically pure (R)-(+)-2-(trifluoromethyl)benzhydrol (R)-(+)-1, a readily available reagent. With respect to the carboxy group, the stereogenic centre is in the beta position in the case of the acids 5a-10a and 12a-16a, and in the alpha position in the case of the acids 17a-20a. The diastereomeric excesses of the corresponding esters 5b-10b and 12b-20b, respectively, were easily determined by means of F-19 NMR. These d.e. values were in very good agreement with the e.e. values of the corresponding acids when the latter were known compounds.
Determination of the enantiomeric excesses of chiral acids by 19F NMR studies of their esters deriving from (R)-(+)-2-(trifluoromethyl)benzhydrol
摘要:
15 Chiral acids were esterified with optically pure (R)-(+)-2-(trifluoromethyl)benzhydrol (R)-(+)-1, a readily available reagent. With respect to the carboxy group, the stereogenic centre is in the beta position in the case of the acids 5a-10a and 12a-16a, and in the alpha position in the case of the acids 17a-20a. The diastereomeric excesses of the corresponding esters 5b-10b and 12b-20b, respectively, were easily determined by means of F-19 NMR. These d.e. values were in very good agreement with the e.e. values of the corresponding acids when the latter were known compounds.
Method of asymmetrically hydrosilylating substrates using catalysts having a ligand of the compound of the formula (I)
wherein
R is optionally substituted alkyl, cycloalkyl, aryl or heteroaryl;
R′ is hydrogen, optionally substituted lower alkyl; and
R″ is hydrogen, halogen, optionally substituted alkyl, hydroxy, amino (e.g., primary, secondary or tertiary), alkenyl;
or an enantiomer thereof; or an enantiomeric mixture thereof with a transition metal. Particularly suitable reactions include the asymmetric hydrosilylation of ketones.
catalysts with a PNP type ligand, the electron-rich chiral PNP ligands have still been rarely reported because of the difficulties in synthesis and the nature of air-sensitivity. Herein, we report a novel chiral PNP ligand (Heng-PNP) with both a rigid backbone and a bulky tert-butyl group on the phospholane motif. We successfully obtained its divalent iron complex. The chiral environment of its Ir(III) complex
Evaluation of Enantiopure <i>N</i>-(Ferrocenylmethyl)azetidin-2-yl(diphenyl)methanol for Catalytic Asymmetric Addition of Organozinc Reagents to Aldehydes
作者:Min-Can Wang、Qing-Jian Zhang、Wen-Xian Zhao、Xiao-Dan Wang、Xue Ding、Tao-Tao Jing、Mao-Ping Song
DOI:10.1021/jo701943x
日期:2008.1.1
catalytic asymmetric addition of organozinc reagents to aldehydes. The asymmetric ethylation, methylation, arylation, and alkynylation of aldehydes achieved enantioselectivity of up to 98.4%, 94.1%, 99.0%, and 84.6% ee, respectively, in the presence of a catalytic amount of chiral N-(ferrocenylmethyl)azetidin-2-yl(diphenyl)methanol. Our results demonstrated further that the four-membered heterocycle-based
Chiral Lithium Amido Aryl Zincates: Simple and Efficient Chemo‐ and Enantio‐Selective Aryl Transfer Reagents
作者:Pauline Chaumont‐Olive、Mathieu Rouen、Gabriella Barozzino‐Consiglio、Amel Ben Abdeladhim、Jacques Maddaluno、Anne Harrison‐Marchand
DOI:10.1002/anie.201813510
日期:2019.3.4
An enantioselective aryl transfer is promoted using chiral tricoordinated lithium amido aryl zincates that are easily accessible reagents and whose chiral appendage is simply recovered for reuse. The arylation reaction is run in good yields (60 % average on twenty substrates) and high enantiomericexcesses (95 % ee average). This occurs whatever the ortho, meta, or para substituent borne by the substrate
New Enantiopure <i>N</i>-Ferrocenylmethyl Azetidin-2-yl(diphenyl)methanol and Its Application in Catalytic Asymmetric Ethylation and Arylation of Arylaldehydes
作者:Min-Can Wang、Mao-Ping Song、Wen-Xian Zhao、Xiao-Dan Wang
DOI:10.1055/s-2006-956474
日期:2006.12
A novel, facile and practical approach to preparation of new enantiopure N-ferrocenylmethyl azetidin-2-yl(diphenyl)methanol has been developed. In the presence of a catalytic amount of the chiral N-ferrocenylmethyl azetidin-2-yl(diphenyl)methanol, the enantioselective ethylation and arylation of arylaldehydes afforded addition products with enantioselectivities of up to 98.4% ee and 95.7% ee, respectively.
我们开发了一种新颖、简便和实用的方法来制备新的对映体纯 N-二茂铁基甲基氮杂环丁烷-2-基(二苯基)甲醇。在手性 N-二茂铁基甲基氮杂环丁烷-2-基(二苯基)甲醇的催化下,芳基醛的对映体选择性乙基化和芳基化得到了加成产物,其对映体选择性分别高达 98.4% ee 和 95.7%ee。