PausonKhand-type reaction mediated by Rh(I) catalysts
Cocyclization of alkynes, alkenes, and carbon monoxide by transition metals (known as PausonKhand reaction when dicobalt octacarbonyl complexes are used) has been accepted as one of the most powerful tools in the synthesis of cyclopentenones. Despite significant progress in the various aspects of the reaction, we still needed new catalysts to expand the scope of the reaction further. We found rhodium (I) catalysts, e.g., RhCl(PPh3)3, trans-RhCl(CO)(PPh3)2, RhCl-(CO)(dppe), and trans-[RhCl(CO)(dppp)]2, were also effective for this transformation. The scope and the efficiencies of the reaction could be tuned and expanded by the choice of catalysts. For example, we were able to devise an enantioselective PK-type reaction and a tandem strategy employing two catalysts in one pot. These results will be presented.