Enhanced enantiocontrol in catalytic metal carbene transformations with dirhodium (II) tetrakis[methyl 2‐oxooxazolidin‐4(S)‐carboxylate], Rh2(4S‐MEOX)4

The synthesis, spectral characteristics, and X‐ray structures for dirhodium(II) tetrakis[methyl 2‐oxooxazolidin‐4(S)‐carboxylate], Rh2(4S‐MEOX)4, and the related dirhodium(II) tetrakis[methyl 5(R)‐methyl‐2‐oxooxazolidin‐4(S)‐carboxylate], 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[methyl 2‐oxopyrrolidine‐5(S)‐carboxylate], 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.