The Mechanism and an Improved Asymmetric Allylboration of Ketones Catalyzed by Chiral Biphenols
作者:David S. Barnett、Philip N. Moquist、Scott E. Schaus
DOI:10.1002/anie.200904715
日期:2009.11.2
Giving it a boost: A mechanistic study of the enantioselective asymmetric titled reaction with allyldiisopropoxyborane catalyzed by chiralbiphenols revealed a key ligand exchange process which liberates isopropyl alcohol. The addition of iPrOH to the reaction increases the overall rate and enantioselectivity. As a result an improved reaction, employing allyldioxaborinane with 1 and tBuOH, resulted
The first example of catalyticenantioselective allylboration and crotylboration of simple ketones is described. High enantioselectivity (up to 93% ee) was obtained using 3 mol % CuF-iPr-DuPHOS as a chiral catalyst and 4.5 mol % La(OiPr)3 as a cocatalyst. Mechanistic studies strongly suggested that the active nucleophile of the present reaction is an allylcopper, and that La(OiPr)3 facilitates the
A general catalyticasymmetricreductivealdolreaction of allenic esters to ketones is described. Two distinct constitutional isomers were selectively produced depending on the reaction conditions. A combination of CuOAc/(R)-DTBM-SEGPHOS/PCy3 as the catalyst predominantly produced γ-cis-products in high yield with excellent enantioselectivity (up to 99% ee). The reaction was applicable to both aromatic
Practical, Broadly Applicable, α-Selective, <i>Z</i>-Selective, Diastereoselective, and Enantioselective Addition of Allylboron Compounds to Mono-, Di-, Tri-, and Polyfluoroalkyl Ketones
作者:Farid W. van der Mei、Changming Qin、Ryan J. Morrison、Amir H. Hoveyda
DOI:10.1021/jacs.7b05011
日期:2017.7.5
accessible unsaturated organoboron compounds serve as reagents. Transformations were performed with 0.5-2.5 mol % of a boron-based catalyst, generated in situ from a readily accessible valine-derived aminophenol and a Z- or an E-γ-substituted boronic acid pinacol ester. With a Z organoboron reagent, additions to trifluoromethyl and polyfluoroalkyl ketones proceeded in 80-98% yield, 97:3 to >98:2 α:γ selectivity
Asymmetric Allylboration of Ketones Catalyzed by Chiral Diols
作者:Sha Lou、Philip N. Moquist、Scott E. Schaus
DOI:10.1021/ja0651308
日期:2006.10.1
Chiral BINOL-derived diols catalyze the enantioselective asymmetricallylboration of ketones. The reaction requires 15 mol % of 3,3‘-Br2-BINOL as the catalyst and allyldiisopropoxyborane as the nucleophile. The reaction products are obtained in good yields (76−93%) and high enantiomeric ratios (95:5−99.5:0.5). High diastereoselectivities (dr ≥ 98:2) and enantioselectivities (er ≥ 98:2) are obtained