Nickel/bis(oxazoline)-catalyzed asymmetric Kumada reactions of alkyl electrophiles: cross-couplings of racemic alpha-bromoketones.
The first asymmetric Kumada reactions of alkyl electrophiles are described, specifically, cross-couplings of racemic alpha-bromoketones with aryl Grignard reagents. Several features of this investigation are of interest. First, the couplings proceed at remarkably low temperature (-40 or -60 degrees C), which enables the asymmetric synthesis of racemization-prone alpha-arylketones. Second, dialkyl ketones undergo enantioselective coupling in good ee and yield. Third, readily available bis(oxazolines) are shown for the first time to be effective ligands for cross-couplings of alkyl electrophiles, thereby opening the door to new opportunities in asymmetric catalysis.
Lou
Sha
S
Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Fu
Gregory C
GC
D017605:Bromine Compounds / Q000737:chemistry; D002384:Catalysis; D007659:Ketones / Q000737:chemistry; D009532:Nickel / Q000737:chemistry*; D010081:Oxazolone / Q000031:analogs & derivatives* / Q000737:chemistry; D013237:Stereoisomerism
D017605:Bromine Compounds; D007659:Ketones; C461065:trifluoromethyloxazolinone; D010081:Oxazolone; D009532:Nickel