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

The enantioselective Mukaiyama‐aldol reaction between 1‐phenyl‐1‐trimethylsilyloxyethene (1) and three pyruvates (2a–c) is catalyzed by the lanthanide triflate complexes of(4S,5S)‐2,6‐bis[5‐phenyl‐4‐(triisopropylsilyloxy)methyl‐1,3‐oxazolin‐2‐yl]pyridine (3). The best catalysts are the LuIII‐ and ScIII‐based complexes that give high yields of (S)‐4a–c and enantiomeric excesses up to 99.5 %. The LaIII‐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)