Iterative Stereospecific Reagent-Controlled Homologation of Pinacol Boronates by Enantioenriched α-Chloroalkyllithium Reagents
摘要:
Reaction of pinacol boronates with putative enantioenriched alpha-chloroalkyllithium species, generated in situ from homochiral alpha-chloroalkylsulfoxides by sulfoxide ligand exchange with t-BuLi in PhMe at -78 degrees C, gave chain-extended boronic ester products with generally excellent stereochemical fidelity. Iteration of this stereospecific reagent-controlled homologation (StReCH) process enabled the programmed synthesis of all four stereoisomers of a stereodiad-containing model system (4-benzyl-1,6-diphenylhexan-2-ol) with er >= 97:3 in all cases.
Nickel-Catalyzed Enantioselective Conjunctive Cross-Coupling of 9-BBN Borates
作者:Matteo Chierchia、Chunyin Law、James P. Morken
DOI:10.1002/anie.201706719
日期:2017.9.18
Catalyticenantioselective conjunctive cross‐coupling between 9‐BBN borate complexes and aryl electrophiles can be accomplished with Ni salts in the presence of a chiral diamine ligand. The reactions furnish chiral 9‐BBN derivatives in an enantioselective fashion and these are converted to chiral alcohols and amines, or engaged in other stereospecific C−C bond forming reactions.
Reagent-Controlled Asymmetric Homologation of Boronic Esters by Enantioenriched Main-Group Chiral Carbenoids
作者:Paul R. Blakemore、Stephen P. Marsden、Huw D. Vater
DOI:10.1021/ol053055k
日期:2006.2.1
and (S)-1-chloro-2-phenylethyllithium (26), generated in situ by sulfoxide ligand exchange from (-)-(R(S),R)-1-chloro-2-phenylethyl p-tolyl sulfoxide (8), effected the stereocontrolled homologation of boronicesters. sec-Alcohols derived from the product boronates by oxidation with basic hydrogen peroxide exhibited % ee closely approaching that of sulfoxide 8 in examples employing Li-carbenoid 26.
We derived a novel equation capable of predicting the degree of enantioselectivity in a catalytic reaction without any knowledge of the reaction mechanism and/or the transition-state structure. and tested the validity of this equation by changing substrates systematically in the lipase or oxazaborolidine-catalyzed reactions A good correlation was observed between the predicted and observed E values, and the stereochemistry of the products Could be predicted correctly in most cases (28 out of 30) (C) 2009 Elsevier Ltd All rights reserved
Chiral vinyl dioxazaborocines in synthesis: asymmetric cuprate additions to β-boronyl acrylates and vinyl sulfones
作者:Christopher N Farthing、Stephen P Marsden
DOI:10.1016/s0040-4039(00)00572-4
日期:2000.5
The first examples of the addition of organometallic reagents to electron deficient boron-substituted olefins are reported. Thus, copper catalysed addition of Grignard reagents to chiral acryloyl and vinylsulfonyl dioxazaborocines, followed by oxidative removal of the boron, gives beta-hydroxy esters and sulfones with asymmetric inductions up to 81 and 95% ee, respectively. (C) 2000 Elsevier Science Ltd. All rights reserved.
Enantioselective, Lewis Base-Catalyzed Carbosulfenylation of Alkenylboronates by 1,2-Boronate Migration
作者:Zhonglin Tao、Kevin A. Robb、Jesse L. Panger、Scott E. Denmark
DOI:10.1021/jacs.8b10288
日期:2018.11.21
A catalytic, enantioselective method for the preparation of chiral, non-racemic, alkylboronic esters bearing two vicinal stereogenic centers is described. The reaction proceeds via a 1,2-migration of a zwitterionic thiiranium-boronate complex to give exclusively anti carbosulfenylation products. A broad scope of aryl groups migrate with good yield and excellent enantioselectivity (up to 99:1 e.r.). Similarly, a range of di- and trisubstituted alkenylboronic esters are competent reaction partners. This method provides access to both secondary and tertiary chiral alkylboronic esters.