Sandwich compound-based planar chiral -heterocyclic carbene (NHC) ligands having a bulky η-cyclopentadienyl-cobalt-η-tetraphenylcyclobutadiene core were developed, and their donor strengths were evaluated by determining the Tolman electronic parameter (TEP) of the Rh dicarbonyl complex. The TEP was high at 2048 cm, as expected for an NHC ligand. The utility of the carbenes as chiral ligands was examined in the Rh-catalyzed asymmetric ring-opening reaction of oxabenzonorbornadienes with benzylamine, and the corresponding products were obtained with moderate enantioselectivities (up to 66% ee).
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http://dx.doi.org/10.1021/acs.joc.4c01347 | DOI Listing |
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