Nitrene-Mediated Enantioselective Intramolecular Olefin Oxyamination to Access Chiral γ-Aminomethyl-γ-Lactones

Attaching a nitrene precursor to an intramolecular nucleophile allows for a catalytic asymmetric intramolecular oxyamination of alkenes in which the nucleophile adds in an endocyclic position and the amine in an exocyclic fashion. Using chiral-at-ruthenium catalysts, chiral gamma-aminomethyl-gamma-lactones containing a quaternary carbon in gamma-position are provided in high yields (up to 99 %) and with excellent enantioselectivities (up to 99 % ee). DFT calculations support the possibility of both a singlet (concerted oxyamination of the alkene) and triplet pathway (stepwise oxyamination) for the formation of the predominant stereoisomer. gamma-Aminomethyl-gamma-lactones are versatile chiral building blocks and can be converted to other heterocycles such as delta-lactams, 2-oxazolidinones, and tetrahydrofurans. Nitrene-mediated asymmetric intramolecular olefin difunctionalization is introduced, in which the nitrene intermediate adds in an unprecedented exocyclic fashion and the nucleophile in an endocyclic fashion. This atom-economic strategy affords chiral gamma-aminomethyl-gamma-lactones in high yields and excellent enantioselectivities and provides access to versatile chiral building blocks.image