Enantioselective Mukaiyama‐Aldol Reaction of Pyruvates and 1‐Phenyl‐ 1‐trimethylsilyloxyethene Catalyzed by Lanthanide/Pybox Complexes

Abstract

Abstract The enantioselective Mukaiyama‐aldol reaction between 1‐phenyl‐1‐trimethylsilyloxyethene ( 1 ) and three pyruvates ( 2a – c ) is catalyzed by the lanthanide triflate complexes of(4 S ,5 S )‐2,6‐bis[5‐phenyl‐4‐(triisopropylsilyloxy)methyl‐1,3‐oxazolin‐2‐yl]pyridine ( 3 ). The best catalysts are the Lu III ‐ and Sc III ‐based complexes that give high yields of ( S )‐ 4a – c and enantiomeric excesses up to 99.5 %. The La III ‐based complex favors the formation of the opposite enantiomer [77 % ee of ( R )‐ 4c ]. The rationale of the stereochemical outcome is proposed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)