Regiocontrol via Electronics: Insights into a Ru‐Catalyzed, Cu‐Mediated Site‐Selective Alkylation of Isoquinolones via a C−C Bond Activation of Cyclopropanols.

A site‐selective C(3)/C(4)‐alkylation of N‐pyridylisoquinolones is achieved by employing C−C bond activation of cyclopropanols under Ru(II)‐catalyzed/Cu(II)‐mediated conditions. The regioisomeric ratios of the products follow directly from the electronic nature of the cyclopropanols and isoquinolones used, with electron‐withdrawing groups yielding predominantly the C(3)‐alkylated products, whereas the electron‐donating groups primarily generate the C(4)‐alkylated isomers. Density functional theory calculations and detailed mechanistic investigations suggest the simultaneous existence of the singlet and triplet pathways for the C(3)‐ and C(4)‐product formation. Further transformations of the products evolve the utility of the methodology thereby yielding scaffolds of synthetic relevance. [ABSTRACT FROM AUTHOR]