Enantioselective Dearomatization of Pyridinium Salts by Copper‐Catalyzed C4‐Selective Addition of Silicon Nucleophiles

Abstract

AbstractA copper‐catalyzed C4‐selective addition of silicon nucleophiles released from an Si−B reagent to prochiral pyridinium triflates is reported. The dearomatization proceeds with excellent enantioselectivity using Cu(CH3CN)4PF6 as the precatalyst and (R,R)‐Ph‐BPE (1,2‐bis[(2R,5R)‐2,5‐diphenylphospholan‐1‐yl]ethane) as the chiral ligand. A carbonyl group at C3 is required for this, likely acting a weak donor group to preorganize and direct the nucleophilic attack towards C4. The resulting 4‐silylated 1,4‐dihydropyridines can be further converted into functionalized piperidine derivatives.