Enantioselective Au(I)/Au(III) Redox Catalysis Enabled by Chiral (P,N)-Ligands

Abstract

Presented herein is the first report of enantioselective Au(I)/Au(III) redox catalysis, enabled by a newly designed hemilabile chiral (P,N)-ligand (ChetPhos). The potential of this concept has been demonstrated by the development of enantioselective 1,2-oxyarylation and 1,2-aminoarylation of alkenes which provided direct access to the medicinally relevant 3-oxyand 3-aminochromans (up to 88% yield and 99% ee). DFT studies were carried out to unravel the enantiodetermining step, which revealed that the stronger trans influence of phosphorus allows selective positioning of the substrate in the C 2 -symmetric chiral environment present around nitrogen, imparting a high level of enantioselectivity.

Hemilabile MIC^N ligands allow oxidant-free Au(i)/Au(iii) arylation-lactonization of γ-alkenoic acids

“…58 Very recently, Shi and Patil groups developed new chiral-hemilabile P^N-ligands to access enantioselective Au(I)/Au(III) catalysis. 59,60 In contrast to the well-known P^N ligands, the use of bidentate C^N or C^O ligands 61 remains scarcely explored, and the few representative examples are depicted in Scheme 1b. Cadierno and Michelet studied the catalytic activity of a (NHC^N)Au(III) complex containing a N-heterocyclic carbene ligand (NHC) with a pyridinium side arm in the cyclization of galkynoic acids (Scheme 1b), 62 while Messerle and coworkers explored the dihydroalkoxylation and hydroamination catalyzed by a Au(III) complex bearing a NHC ligand with two pendant pyrazole arms (Scheme 1b).…”

“…58 Very recently, Shi and Patil groups developed new chiral-hemilabile P^N-ligands to access enantioselective Au( i )/Au( iii ) catalysis. 59,60…”

Ligand-Enabled Gold-Catalyzed C(sp2)–S Cross-Coupling Reactions

“…It was Bourissou and co-workers who developed this novel ligand-enabled strategy to access the Au­(I)/Au­(III) redox cycle by facilitating the key oxidative addition of aryl halides onto a gold­(I) complex by using hemilabile (P, N) ligand (MeDalPhos) . They have demonstrated the utility of this strategy by realizing the first gold-catalyzed C–C cross-coupling reactions of aryl halides with electron-rich arenes to afford biaryls (Scheme a). , This ligand-enabled approach has proven to be very promising in accomplishing various cross-coupling and 1,2-difunctionalization reactions. As far as cross-coupling reactions are concerned, our group and Bourissou’s group reported C­(sp 2 )–N cross-coupling reactions of aryl iodides and anilines by using this ligand-enabled technique (Scheme b).…”

Gold-Catalyzed Cross-Coupling and 1,2-Difunctionalization ­Reactions: A Personal Account

“…Aminoarylation of alkenes with external amines Very recently, we developed the first Au(I)/Au(III) catalyzed enantioselective 1,2-aminoarylation and 1,2-oxyarylation reaction by using newly designed 'ChetPhosAuCl' gold complex (Scheme 15). 35 The 1,2-aminoarylation was performed in the presence of ChetPhosAuCl (5 mol%), AgSbF6 (1.15 equiv), and K3PO4 (0.1 equiv) at 80 °C to produce desired products 15b (upto 86% yield and 99% ee). While, the 1,2-oxyarylation carried out without base in the presence of ChetPhosAuCl (5 mol%), AgOTf (1.05 equiv) at 80 °C furnishes the desired products 15c (up to 88% yield and 99% ee).…”