Co-catalyzed mild and chemoselective reduction of phenyl esters with NaBH4: a practical synthesis of (R)-tolterodine

CoCl2 catalyzes effectively the chemoselective reduction of phenyl carboxylic esters to the corresponding saturated alcohols in high yields using NaBH4 at ambient conditions. By employing this methodology, the synthesis of (R)-tolterodine, a muscarinic receptor antagonist, has been achieved in high yield and optical purity.