Toolbox approach to the search for effective ligands for catalytic asymmetric Cr-mediated coupling reactions.
Chromium catalysts derived from chiral sulfonamides represented by A effect the couplings of aldehydes with vinyl, allyl, or alkyl halides. With three distinct sites for structural modification, A affords access to a structurally diverse pool of chiral sulfonamides. The Cr catalysts derived from these sulfonamides exhibit a broad range of catalyst-substrate matching profiles. A strategy is presented to search for a satisfactory chiral sulfonamide for a given substrate. In order to demonstrate the generality and effectiveness of this approach, five diverse C-C bond-forming cases have been selected from the halichondrin synthesis. For each of the cases, two ligands have been deliberately searched for, to induce the formation of (R)- and (S)-alcohols, respectively, at the arbitrarily chosen efficiency level of ">or=80% yield with >or=20:1 stereoselectivity in the presence of <or=20 mol % of a Cr catalyst". For 9 out of the 10 cases studied, a satisfactory catalyst has been found within this pool of sulfonamides. Even for the remaining case, a Cr catalyst inducing stereoselectivity up to 8:1 has been identified.
Guo
Haibing
H
Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, USA.
Dong
Cheng-Guo
CG
Kim
Dae-Shik
DS
Urabe
Daisuke
D
Wang
Jiashi
J
Kim
Joseph T
JT
Liu
Xiang
X
Sasaki
Takeo
T
Kishi
Yoshito
Y
D002384:Catalysis; D002857:Chromium / Q000737:chemistry*; D008024:Ligands; D008958:Models, Molecular; D015394:Molecular Structure; D013237:Stereoisomerism; D013449:Sulfonamides / Q000737:chemistry
D008024:Ligands; D013449:Sulfonamides; D002857:Chromium