Synthesis of 1,2-Disubstituted Cyclopentadienes from Alkynes Using a Catalytic Haloallylation/Cross-Coupling/Metathesis Relay.

A three-step method based on Pd-catalyzed haloallylation of alkynes, Pd-catalyzed cross-coupling, and Ru-catalyzed ring-closing metathesis constitutes a new and short approach to variety of 1,2-substituted cyclopentadienes. The scope of the method is broad with respect to different substituents (alkyl, aryl, metallocenyl, and other substituents as well as their combinations are tolerated), and all steps proceeded with sensible yields. As a demonstration of product utility, several of the prepared cyclopentadienes were converted into the corresponding ferrocenes.