Regioselective Synthesis of β-Aryl- and β-Amino-Substituted Aliphatic Esters by Rhodium-Catalyzed Tandem Double-Bond Migration/Conjugate Addition

Rhodium-phosphite catalysts were found to effectively mediate double-bond migrations within unsaturated esters. Once the double-bond is in conjugation with the carboxylate group, they also catalyze the Michael addition of carbon and nitrogen nucleophiles. In the presence of these catalysts, unsaturated carboxylates enter a dynamic equilibrium of positional and geometrical double-bond isomers. The conjugated species are continuously removed through 1,4-additions with formation of beta-amino esters or beta-arylated products, depending on the nucleophile employed. The applicability of both protocols to a range of substrates, such as fatty esters of different chain lengths and double-bond positions, and several nucleophiles including arylborates and primary and secondary amines, is demonstrated.