Ruthenium-Catalyzed Synthesis of Isoquinolones with 8‑Aminoquinoline as a Bidentate Directing Group in C–H Functionalization

Ruthenium-catalyzed
oxidative annulation of N-quinolin-8-yl-benzamides
with alkynes in open air has been achieved using 8-aminoquinolinyl
moiety as a bidentate directing group in the presence of Cu­(OAc)2·H2O as an oxidant. This reaction offers a
broad substrate scope, and both symmetrical and unsymmetrical alkynes
can be applied. High regioselectivity was achieved in the case of
unsymmetrical (aryl)­alkynes. Reaction with heteroaryl amides was also
successful in this catalytic process. A ruthenium-N-quinolin-8-yl-benzamide complex was isolated in the absence of alkyne;
in the absence of both N-quinolin-8-yl-benzamide
and alkyne, in contrast to literature, only the monoacetate
complex RuCl­(OAc)­(p-cymene), but not the bis-acetate
complex Ru­(OAc)2(p-cymene), was isolated.
These data suggest that this reaction may proceed via N,N-bidentate chelate complex. Key products were
characterized by X-ray crystallography.