ABSTRACT
An efficient oxidative C-H alkynylation of N-carbamoyl tetrahydroisoquinolines mediated by a TEMPO oxoammonium salt has been established. A variety of electronically varied N-carbamoyl tetrahydroisoquinolines reacted with a range of alkynyl potassium trifluoroborates smoothly under mild metal-free conditions. Dihydroisoquinolines were also suitable components for the reaction. The synthetic applicability of the method for facile access to structurally diverse bioactive molecules was further demonstrated.
ABSTRACT
The first non-enzymatic redox deracemization method using molecular oxygen as the terminal oxidant has been described. The one-pot deracemization of ß,γ-alkynyl α-amino esters consisted of a copper-catalyzed aerobic oxidation and chiral phosphoric acid-catalyzed asymmetric transfer hydrogenation with excellent functional group compatibility. By using benzothiazoline as the reducing reagent, an exclusive chemoselectivity at the C[double bond, length as m-dash]N bond over the C[triple bond, length as m-dash]C bond was achieved, allowing for efficient deracemization of a series of α-amino esters bearing diverse α-alkynyl substituent patterns. The origins of chemo- and enantio-selectivities were elucidated by experimental and computational mechanistic investigation. The generality of the strategy is further demonstrated by efficient deracemization of ß,γ-alkenyl α-amino esters.
ABSTRACT
A practical and modular three-component alkene oxyarylation with benzoquinone and H2O to rapidly access C3-substituted dihydrobenzofurans has been developed. The (NH4)2S2O8-mediated redox-relay process has an excellent regioselectivity and functional group tolerance and exhibits a broad scope of simple alkenes, rapidly furnishing a variety of the substructures that would require multiple steps to prepare with traditional methods. Mechanistic studies revealed a dual role of benzoquinone serving as both the arylation agent and the origin of dihydroquinone for the reductive cyclization step.