Selective reduction of stereodefined cyclopropyl substituted acrylate esters to the corresponding propionate esters

Stereodefined cyclopropyl substituted acrylate esters were selectively reduced to the corresponding propionate esters by sodium borohydride in methanol/DMF with a catalytic amount of CoCl2 without the opening of the cyclopropane ring. The configuration and chirality of the stereodefined cyclopropyl function were retained in the reaction. Combined with the cross-coupling reaction of stereodefined cyclopropylboronic acids with bromoacrylate esters or alkenyl triflates, the reaction method provides a novel route to stereodefined 3-cyclopropyl propionate ester, an important subunit existing in a wide range of natural compounds.