A challenging direct asymmetric hydrogenation of (E)-2-oxo-4-arylbut-3-enoic acids to give 2-hydroxy-4-arylbutanoic acids (85.4-91.8% ee) was achieved with a Ru catalyst based on SunPhos as the chiral ligand. Further investigation of the reaction revealed that partial isomerization of 2-hydroxy-4-arylbutenoic acids was involved in the hydrogenation process. Employing the reaction conditions to the hydrogenation of 2-oxo-4-phenylbutanoic acid resulted in better enantioselectivity (91.8% ee) and efficiency (TON = 2000, TOF = 200 h(-1)), which offers a useful method for the synthesis of a common intermediate for ACE inhibitors.
Siteselective and Enantiocomplementary C(sp<sup>3</sup>)–H Oxyfunctionalization for Synthesis of α-Hydroxy Acids
Oxyfunctionalization of abundant carboxylic acids represents a direct approach to synthesizing α-hydroxyacids, which are valuable intermediates of various active pharmaceutical ingredients. Although ideal, the transformation is yet to be accomplished. Herein, enantiocomplementary C(sp3)–H oxyfunctionalization for the synthesis of α-hydroxyacids was realized by a cooperative strategy of substrate