Synthetic Applications of Synergism using Catalytic Binuclear Elimination Reactions. Further Examples of Rhodium-Manganese and Rhodium-Rhenium-Catalyzed Hydroformylations

摘要

Synergism has been previously observed in both rhodium-manganese- and rhodium-rhenium-catalyzed hydroformylation. Furthermore, detailed in situ spectroscopic investigations have conclusively shown that the phenomenological origin of this synergistic effect is catalytic binuclear elimination (J. Am. Chem. Soc. 2003, 125, 5540-5548; 2007, 129, 13327-13334). In the present contribution, further substrates are used in the hydroformylation reaction with both rhodium-manganese and rhodium-rhenium. In situ spectroscopic studies show that (i) significant rate enhancements occur in the mixed metal systems with the new substrates and (ii) the organo-metallics present in the active systems, and their con-centration profiles are consistent with those present in the previously studied catalytic binuclear elimination reactions (CBER). It is therefore concluded that catalytic binuclear elimination is a rather general mechanism in mixed metal hydroformylations and is rather independent of the substrates used. Further discussion is given to mechanistic aspects, synthetic efficiency, and the possibility that such synergistic effects might be useful to other classes of organic syntheses.