Trinuclear Borane (B3H7)-Mediated Selective C4–H Alkylation and Phosphonation of Quinolines and Tetrahydroquinolines

Herein, we report a method for the regioselective alkylation and phosphonation of quinoline C4–H via a B3H7-mediated nucleophilic addition of Turbo Grignard reagents and phosphine oxide anions to quinolines bearing different substituents, affording the 4-alkyl and 4-phosphoryl quinolines and tetrahydroquinolines after one-pot oxidation or reduction. The results indicate that coordination of the B3H7 group can activate substrates toward a potential 1,4-dearomative addition and subtly control the regioselectivity by preventing the 1,2-dearomative addition.