Enantioselective, nickel-catalyzed Suzuki cross-coupling of quinolinium ions

Abstract

Quinolinium ions are engaged in an asymmetric, Ni-catalyzed Suzuki cross-coupling to yield 2-aryl- and 2-heteroaryl-1,2-dihydroquinolines. Key to the development of this method is the use of a Ni(II) precatalyst that activates without the need for strong reductants or high temperatures. The Ni-iminium activation mode is demonstrated as an exceptionally mild pathway to generate enantioenriched products from racemic starting materials.

Figure 1

Ni-iminium activation mode for asymmetric catalysis.

Figure 2

Nucleophile Scope^{a,b,c a} Reactions run on a 0.5 mmol scale at 0.01 M under an N₂ atmosphere. ^b Isolated yields (average of two runs). ^c Enantiomeric excess determined by chiral HPLC (average of two runs). ^d 10 mol % [(methallyl)NiCl]₂, 30 mol % L4, 30 mol % NaOPh·3H₂O, 48 h.

Figure 3

Electrophile Scope^{a,b,c a} Reactions run on a 0.5 mmol scale at 0.01 M under an N₂ atmosphere. ^b Isolated yields (average of two runs). ^c Enantiomeric excess determined by chiral HPLC (average of two runs).