Asymmetric Ring Opening of Benzo‐7‐oxabicyclo[2.2.1]heptadienes with Cationic Rhodium Complexes

Abstract

Abstract:The efficient design of stereochemically challenging ring systems by ring opening of heterobicyclic alkenes has become a very important reaction in the chemistry of C À C and C À X bond formation. By using the hitherto applied in situ technique for the generation of the m 2 -bridged, dimeric neutral rhodium complexes, however, the catalytically active species and its concentration remained unidentified. Furthermore, the reaction temperature is at least 80 8C. The application of cationic rhodium(I) solvate complexes (that no longer contain blocking diolefins)shows that a much greater activity and enantioselectivity for the synthesis of 1,2-dihydro-1-naphthols can be reached than was described so far, even at ambient temperature. NMR spectroscopy and X-ray analysis show that a product inhibition during the ring opening reaction takes place that is independent of the nucleophile.

In Situ Synthesis of Neutral Dinuclear Rhodium Diphosphine Complexes [{Rh(diphosphine)(μ2‐X)}2]: Systematic Investigations

“…Like the ligands discussed above, PPF‐P t Bu 2 reacts with 2 in MeOH to give a cationic rhodium species [Rh(PPF‐P t Bu 2 )(nbd)] + ,36 the molecular structure of which has been previously reported in the literature 6b…”

Activation, Deactivation and Reversibility Phenomena in Homogeneous Catalysis: A Showcase Based on the Chemistry of Rhodium/Phosphine Catalysts

“…This is an important process for the formation of C-C and C-X bonds which gives access to pharmaceutically relevant hydronaphatelenes. The efficiency and enantioselectivity of the process as originally developed [118] could be improved by using the preformed solvent complex [Rh((R,S)-PPF-P(t-Bu) 2 )(THF) 2 ] + instead of the in situ generated dimeric species [Rh(((R,S)-PPF-P(t-Bu) 2 )(µ 2 -Cl)] 2 [119].…”

Rh chemistry through the eyes of theory

“…However, Rh(II) species play an important role for CH‐activation processes, such as carboxylate‐bridged Rhodium dimers. T‐shaped 14 electron Rhodium(I) complexes have been proposed in catalytic reactions starting with dimeric Rhodium(I) species; in some cases, they have been characterized by DFT computations . Trigonal bipyramidal pentacoordinated Rhodium(I) complexes have been discussed in the context of ligand exchange in catalytically active species .…”