Co(III)-catalyzed highly regio-and stereoselective direct C6 olefination of 2-pyridones with alkynes has been developed with the assistance of chelation. Upon variation of the reaction conditions, 2-pyridones react well with diaryl alkynes via a C6 olefination/directing group migration pathway to give the tetrasubstituted 6-vinyl-2-pyridones, but the C6−H olefination with terminal alkynes works effectively to afford only the C6-olefinated 2-pyridones. A judicious choice of a solvent and an additive is crucial for catalysis. The protocols feature 100% atom economy, excellent site selectivity, high stereoselectivity, an ample substrate scope, and good compatibility of functional groups. Synthetic applications are demonstrated, and experimental studies and density functional theory calculations are conducted to gain mechanistic insight into the two transformations.
Cp*Rh(III)‐catalyzed chelation‐assisted direct C−H bond functionalization of 1‐(2‐pyridyl)‐2‐pyridones with internal alkynes that can be controlled to give three different products in good yields has been realized. Depending on the reaction conditions, solvents and additives, the reaction pathway can be switched between alkenylation, alkenylation/directing group migration and rollover annulation. These reaction manifolds allow divergent access to a variety of valuable C6‐alkenylated 1‐(2‐pyridyl)‐2‐pyridones, (Z)‐6‐(1,2‐diaryl‐2‐(pyridin‐2‐yl)vinyl)pyridin‐2(1H)‐ones and 10H‐pyrido[1,2‐a][1,8]naphthyridin‐10‐ones from the same starting materials. These protocols exhibit excellent regio‐ and stereoselectivity, broad substrate scope, and good tolerance of functional groups. A combination of experimental and computational approaches have been employed to uncover the key mechanistic features of these reactions.
A Mn(I)-catalyzed chelation-assisted direct C6À H alkenylation of 2-pyridones with both terminal and internal alkynes in a highly regio-and stereo-selective manner has been developed. The catalytic system consisting of Mn(CO) 5 Br catalyst and KOAc additive allows 1-(2-pyridyl)-2-pyridones to undergo alkenylation with various terminal alkynes in methyl tert-butyl ether (MTBE) to furnish the C6-alkenylated 2-pyridone products in high yields, and the alkenylation with internal alkynes occurs in CH 2 Cl 2 at increased catalyst and additive loadings. Mechanistic studies suggest the involvement of a five-membered organomanganese as the key intermediate in the catalytic cycle.
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