title: Enantioselective copper catalysed C-H insertion reaction of 2-sulfonyl-2-diazoacetamides to form γ-lactams.
abstract: The first examples of asymmetric copper-catalysed intramolecular C-H insertion reactions of 2-sulfonyl-2-diazoacetamides are described; trans γ-lactams with up to 82% ee are achieved with the CuCl2-bisoxazoline-NaBARF catalyst system. The reactions generally display high efficiency and high trans selectivity, and also a strong regiochemical preference for insertion to lead to the formation of 5-membered rings over 4-membered rings. In cases where there are competing C-H insertion pathways available, to form sulfolanes or thiopyrans, only the insertion into the amide chain to form γ-lactams is observed. With phenylsulfonyl derivatives, a minor competing C-H insertion pathway leading to β-lactams is seen; interestingly, changing the identity of the copper ligand changes the product ratio of β/γ-lactams. The copper catalysed reactions compare favorably in terms of efficiency and enantioselectivity to the corresponding reactions catalysed by commercially available chiral rhodium catalysts.
authors.affiliation: Department of Chemistry, Analytical and Biological Chemistry Research Facility, Synthesis and Solid State Pharmaceutical Centre, University College Cork, Cork, Ireland.
authors.forename: Leslie Ann
authors.initials: LA
authors.lastname: Clarke
authors.forename: Aoife
authors.initials: A
authors.lastname: Ring
authors.forename: Alan
authors.initials: A
authors.lastname: Ford
authors.forename: Abhijeet S
authors.initials: AS
authors.lastname: Sinha
authors.forename: Simon E
authors.initials: SE
authors.lastname: Lawrence
authors.forename: Anita R
authors.initials: AR
authors.lastname: Maguire
mesh_terms: D002244:Carbon / Q000737:chemistry*; D002384:Catalysis; D003300:Copper / Q000737:chemistry*; D003979:Diazonium Compounds / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry*; D007769:Lactams / Q000737:chemistry*; D013237:Stereoisomerism; D013379:Substrate Specificity
chemical_list: D003979:Diazonium Compounds; D007769:Lactams; C011752:diazoacetamide; D002244:Carbon; D003300:Copper; D006859:Hydrogen