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, Rh-2(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. Chirality 26:764-774, 2014. (c) 2014 Wiley Periodicals, Inc.