Stereoselective synthesis of 3-substituted phtalides via asymmetric transfer hydrogenation using well-defined ruthenium catalysts under neutral conditions

Abstract

The asymmetric transfer hydrogenation of methyl 2-acylbenzoates and 2-propyl 3-acetylpyridine-2-carboxylate in 2-propanol, in the absence of base, with presynthesized Ru-{β-amino alcohol) or Ru-{TsDPEN} true catalysts provides 3-alkylphtalides in high yields and 92–97% ee. The procedure is, however, not as efficient for the preparation of optically active 3-phenylphtalide.