Enhanced enantiocontrol in catalytic metal carbene transformations with dirhodium(II) tetrakis, Rh2(4S-MEOX)4

Article abstract of DOI:10.1002/recl.19951140407

The synthesis, spectral characteristics, and X-ray structures for dirhodium(II) tetrakis, Rh2(4S-MEOX)4, and the related dirhodium(II) tetrakis, Rh2(4S-THREOX)4, are reported.Comparison is made between these 2-oxooxazolidin-ligated dirhodium(II) catalysts for metal carbene transformations and those with comparable 2-oxopyrrolidine ligands, especially dirhodium(II) tetrakis, Rh2(5S-MEPY)4.Structure-selectivity comparisons reveal that Rh2(4S-MEOX)4 provides higher enantiocontrol and, in some cases, higher diastereocontrol than Rh2(5S-MEPY)4 in intramolecular carbon-hydrogen insertion reactions of sterically demanding diazoacetates and diazoacetamides and is the catalyst of choice for highly enantioselective diazodecomposition of adamantyl diazoacetates and N-(tert)butyldiazoacetamides.The structurally analogous Rh2(4S-THREOX)4 is nearly identical with Rh2(4S-MEOX)4 in its overall effect on selectivity.The net advantage of Rh2(4S-MEOX)4 lies in its wider openness for metal carbene transformations.