Base-Free Conditions for Rhodium-Catalyzed Asymmetric Arylation To Produce Stereochemically Labile α-Aryl Ketones.
The asymmetric arylation of 2,2-dialkyl cyclopent-4-ene-1,3-diones with aryl boronic acids was found to be efficiently catalyzed by a chiral diene-rhodium μ-chloro dimer, [{RhCl((R)-diene*)}2 ], in the absence of bases in toluene/H2 O to give 2,2-dialkyl 4-aryl cyclopentane-1,3-diones in high yields with high enantioselectivity. Such compounds can not be obtained with high enantiomeric purity under the standard basic conditions used for rhodium-catalyzed asymmetric arylation because the α-aryl ketone products undergo racemization under the basic conditions.
Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore, 117543, Singapore.
Xiaowei
X
Dou
Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore, 117543, Singapore. chmlyx@nus.edu.sg.
Yixin
Y
Lu
Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore, 117543, Singapore. chmtamh@nus.edu.sg, tamioh@imre.a-star.edu.sg.|Institute of Materials Research and Engineering, A*STAR, 2 Fusionopolis Way, Singapore, 138634, Singapore. chmtamh@nus.edu.sg, tamioh@imre.a-star.edu.sg.
Tamio
T
Hayashi
asymmetric arylation; chiral diene ligands; racemization; rhodium; α-aryl ketones