Cyanoesterification of norbornenes catalyzed by palladium: facile synthetic methodology to introduce cyano and ester functionalities via direct carbon-carbon bond cleavage of cyanoformates

Addition of cyanoformates (NC-COOR) to norbornene at 110 °C in the presence of Pd(PPh₃)₄ (10 mol %) as a catalyst affords with high selectivity the corresponding doubly functionalized polar norbornane derivatives bearing both cyano and ester groups. By using benzonorbornadiene and norbornadienes as the substrates, the reaction can be extended to synthesis of various functionalized norbornene derivatives in moderate to excellent yields. In most cases alkyl groups such as methyl, ethyl, n-propyl, iso-propyl, n-butyl, tert-butyl, and benzyl in the ester functionalities are applicable to the reactions. Oxidative addition of cyanoformates to Pd(0), insertion of norbornenes, and reductive elimination of the corresponding adducts constitute the proposed catalysis pathway.