Rh2(S-1,2-NTTL)4: A Novel Rh2(S-PTTL)4 Analog With Lower Ligand Symmetry for Asymmetric Synthesis of Chiral Cyclopropylphosphonates

A new series of dirhodium(II) tetracarboxylate was derived from N-1,2-naphthaloyl-(S)-amino acid ligands. In terms of enantioselectivity, Rh2(S-1,2-NTTL)4 ( 3a) derived from N-1,2-naphthaloyl-(S)-tert-leucine, was the best-performing catalyst among the new series in the enantioselective synthesis of cyclopropylphosphonate derivatives (up to > 99% enantiomeric excess). A predictive model was proposed to justify the observed high enantiomeric induction exhibited by Rh 2(S-1,2-NTTL)4 with donor-acceptor phosphonate carbenoids.