The asymmetric conjugate addition of arylboronic acids to substituted and unsubstituted β- pyrazol-1-yl (E)-tert-butyl acrylates 4 catalyzed by 5 mol% of the Rh (I)/diene 2a catalyst provided the corresponding addition products in 44–98% yield and 91–> 99.5% ee. The method was applied to the formal synthesis of (3 S)-3-aryl-3-(pyrazol-1-yl) propanoic acid 1b with agonistic activity toward the human GPR40 G-protein coupled receptor.
