Cycloalkene Carbonitriles in Rhodium-Catalyzed 1,4-Addition and Formal Synthesis of Vabicaserin.

Cycloalkenes with exocyclic acceptor substituents still remain challenging substrates for enantioselective rhodium-catalyzed 1,4-addition. Cycloalkene carbonitriles and carboxylates have been investigated, and a highly diastereo- and enantioselective protocol for 1,4-addition to cyclopentene and cycloheptene carbonitrile has been developed. This new asymmetric transformation was subsequently applied in the asymmetric formal synthesis of the drug candidate Vabicaserin.