title: Rh(2)(S-PTTL)(3)TPA-A Mixed Ligand Dirhodium(II) Catalyst for Enantioselective Reactions of α-Alkyl-α-Diazoesters.
abstract: Herein we report the synthesis of the mixed ligand paddlewheel complex dirhodium(II) tris[N-phthaloyl-(S)-tert-leucinate] triphenylacetate, Rh(2)(S-PTTL)(3)TPA, the structure of which bears similarity to the chiral crown complex Rh(2)(S-PTTL)(4). Rh(2)(S-PTTL)(3)TPA engages substrate classes (aliphatic alkynes, silylacetylenes, α-olefins) that are especially challenging in intermolecular reactions of α-alkyl-α-diazoesters, and catalyzes enantioselective cyclopropanation, cyclopropenation, and indole C-H functionalization with yields and enantioselectivities that are comparable or superior to Rh(2)(S-PTTL)(4). Mixing ligands on paddlewheel complexes offers a versatile handle for diversifying catalyst structure and reactivity. The results described herein illustrate how mixed ligand catalysts can create new opportunities for the optimization of catalytic asymmetric processes.
authors.affiliation: Brown Laboratory, Department of Chemistry and Biochemistry, Newark, DE 19803, USA. ; Tel: +1 302 831 0191.
authors.forename: David T
authors.initials: DT
authors.lastname: Boruta
authors.forename: Olga
authors.initials: O
authors.lastname: Dmitrenko
authors.forename: Glenn P A
authors.initials: GP
authors.lastname: Yap
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Fox