Copper-Catalyzed Conjugate Additions of Alkylboranes to Imidazolyl α,β-Unsaturated Ketones: Formal Reductive Conjugate Addition of Terminal Alkenes
作者:Hirohisa Ohmiya、Mika Yoshida、Masaya Sawamura
DOI:10.1021/ol102819k
日期:2011.2.4
Conjugateaddition of alkylboron compounds (alkyl-9-BBN) to imidazol-2-yl α,β-unsaturated ketones proceeded in the presence of a catalytic amount (10 mol %) of CuCl, 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes), and t-BuOK. The alkylboranes are available through alkene hydroboration, and thus the overall process represents a reductive conjugateaddition of alkenes to enone derivatives. A
A metal-coordination-based high performance asymmetric catalyst utilizing metal centrochirality as the sole element of chirality is reported. The introduced substitutionallylabile chiral-at-metal octahedral iridium(III) complex exclusively bears achiral ligands and effectively catalyzes the enantioselective Friedel-Crafts addition of indoles to α,β-unsaturated 2-acyl imidazoles (19 examples) with
Enantioselective Nitrone Cycloadditions of α,β-Unsaturated 2-Acyl Imidazoles Catalyzed by Bis(oxazolinyl)pyridine−Cerium(IV) Triflate Complexes
作者:David A. Evans、Hyun-Ji Song、Keith R. Fandrick
DOI:10.1021/ol061223i
日期:2006.7.1
Enantioselective nitrone cycloadditions with, ss-substituted alpha,ss-unsaturated 2-acyl imidazoles catalyzed by bis(oxazolinyl) pyridine-cerium(IV) triflate complexes 1 have been reported. The isoxazolidine products were efficiently transformed into densely functionalized, ss'- hydroxy-ss-amino acid derivatives.
Enantioselective Friedel−Crafts Alkylations of α,β-Unsaturated 2-Acyl Imidazoles Catalyzed by Bis(oxazolinyl)pyridine−Scandium(III) Triflate Complexes
作者:David A. Evans、Keith R. Fandrick、Hyun-Ji Song
DOI:10.1021/ja052433d
日期:2005.6.1
An enantioselective Friedel−Craftsalkylation with α,β-unsaturated 2-acyl imidazoles and electron-rich aromatic nucleophiles catalyzed by bis(oxazolinyl)pyridine−scandium(III) triflate complexes has been accomplished. These α,β-unsaturated 2-acyl imidazoles are effective electrophiles for the Friedel−Crafts reaction. The resulting adduct 2-acyl imidazole is easily converted to amides, esters, carboxylic
Enantioselective Friedel−Crafts Alkylations Catalyzed by Bis(oxazolinyl)pyridine−Scandium(III) Triflate Complexes
作者:David A. Evans、Keith R. Fandrick、Hyun-Ji Song、Karl A. Scheidt、Risheng Xu
DOI:10.1021/ja072976i
日期:2007.8.1
The enantioselective Friedel-Crafts addition of a variety of indoles catalyzed by bis(oxazolinyl)pyridine-scandium(III) triflate complexes (Sc(III)-pybox) was accomplished utilizing a series of beta-substituted alpha,beta-unsaturated phosphonates and alpha,beta-unsaturated 2-acyl imidazoles. The acyl phosphonate products were efficiently transformed into esters and amides, whereas the acyl imidazole adducts were converted to a broader spectrum of functionalities such as esters, amides, carboxylic acids, ketones, and aldehydes. The sense of stereoinduction and level of enantioselectivity were found to be functions of the size of the substrate employed, the substitution on the ligand, and the catalyst loading. Molecular modeling of the catalyst with the bound substrates was performed based on the crystal structures of the catalyst complexes and the sense of stereoinduction observed in the addition reaction. Nonlinear effects over a range of catalyst concentrations implicate a mononuclear complex as the active catalyst.