Abstract
Transition-metal-catalyzed hydroamination of unsaturated hydrocarbons is an appealing synthetic tool for the construction of high value-added chiral amines. Despite significant progress in the asymmetric hydroamination of alkenes, allenes, and 1,3-dienes, asymmetric hydroamination of 1,6-enynes or 1,7-enynes remains rather limited due to the enormous challenges in controlling the chemoselectivity and stereoselectivity of the reaction. Herein, we report a Ni-catalyzed chemo- and enantioselective reductive cyclization/amidation and amination of 1,6-enynes and 1,7-enynes using dioxazolones or anthranils as nitrene-transfer reagents. This mild, modular, and practical protocol provides rapid access to a variety of enantioenriched 2-pyrrolidone and 2-piperidone derivatives bearing an aminomethylene group at the 4-position in good yields (up to 83 %) with excellent enantioselectivities (46 examples, up to 99 % ee). Mechanistic experiments and density functional theory calculations indicate that the reaction is initiated by hydronickelation of alkynes followed by migratory insertion into alkenes, rather than by a [2+2+1] oxidative addition process of nickel to alkenes and alkynes.
Published Version
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