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DOI: 10.1055/s-2002-34861
A New and Practical Procedure for Asymmetric 1,4-Addition of Boronic Acids to α,β-Unsaturated Ketones Catalyzed by Rh-(R)-Digm-BINAP System
Publication History
Received
12 July 2002
Publication Date:
21 October 2002 (online)


Abstract
Rh-catalyzed C-C bond asymmetric formation under basic conditions in organoaqueous or alcoholic solvents has been described using the atropoisomeric water-soluble ligand (R)-Digm-BINAP. The addition of phenylboronic acid to cyclohexenone has been efficiently optimized leading to quantitative yield and enantiomeric excesses up to 98% using 1-3 mol% catalyst. Easy product-catalyst separation has been found using ethylene glycol as the reaction solvent. Other α,β-unsaturated ketones and boronic acids could be engaged in the 1,4-addition. The mole fraction of the catalyst could be decreased to 0.005% with still acceptable ee. A TON of 13200 was obtained.
Key words
chiral cationic water-soluble ligand - boronic acids - α,β-unsaturated ketones - asymmetric C-C bond formation - rhodium