Asymmetric Friedel-Crafts alkylation of activated benzenes with methyl (E)-2-oxo-4-aryl-3-butenoates catalyzed by [Pybox/Sc(OTf)3]

The asymmetric Friedel-Crafts reaction between methyl (E)-2-oxo-4-aryl-3-butenoates (la-c) and activated benzenes (2a-d) has been efficiently catalyzed by the Sc-III triflate complex of (4'S,5'S)-2,6-bis[4'-(triisopropylsilyl) oxymethyl-5'-phenyl-1',3'-oxazolin-2'-yl]pyridine (pybox 3). The 4,4-diaryl-2-oxo-butyric acid methyl esters (4) are usually formed in good yields and the enantioselectivity is up to 99% ee. The sense of the stereoinduction can be rationalized with the same octahedral complex (10) between 1, pybox 3 and Sc triflate already proposed for other reactions involving pyruvates, and catalyzed by the same complex. (C) 2010 Elsevier Ltd. All rights reserved.