Palladium-catalyzed direct alkenylation of 4-hydroxy-2-pyridones

Abstract

The first direct 3-alkenylation of N-substituted 4-hydroxy-2-pyridones with unactivated alkenes is reported through a palladium acetate catalyzed, oxidative coupling.

Transition Metal Mediated C–H Activation of 2‐Pyrones, 2‐Pyridones, 2‐Coumarins and 2‐Quinolones

“…The direct alkenylation of 2‐pyridones was independently reported by Zografos (Scheme ) . In this case, under similar conditions, 3‐alkenyl‐4‐hydroxy‐2‐pyridones are also formed when using higher substituted alkenes.…”

“…The direct alkenylation of 2-pyridones was independently reported by Zografos (Scheme 23). [40] In this case, under similar conditions, 3-alkenyl-4-hydroxy-2-pyridones are also formed when using higher substituted alkenes. However, when terminal alkenes are used, intermediate Pd-O bond formation leads to extended reaction, and the efficient production of furo-[3,2-c]-pyridinones.…”

Pd-catalyzed Intermolecular Dehydrogenative Heck Reactions of Six-membered Heteroarenes

“…A domino reaction arose from 4-hydroxy-1-methylpyridin-2(1H)-one and 1-hexene leading to cyclisation products (Eq. 15) [61]. Homocoupling of the aromatic substrate may be a side-product.…”

“…The catalytic cycle depicted in Scheme 6, which is inspired by the proposal of Zografos and co-workers [61], involves C3 palladation of the substrate giving 6A. Coordination of 1-hexene followed by insertion into the C-Pd bond of 6B gives 6C and/or 6D.…”

“…15) remains undetermined. On the basis of possible change of the insertion regioselectivity of alkenes into the C-Pd bond with the nature, cationic versus neutral, of Pd intermediates [62,63], the authors proposed "neutral-type mechanism in acetonitrile which changes to cationic when reaction is conducted in dioxane" [61]. We are rather sceptic towards this hypothesis because acetonitrile and dioxane have similar coordinating properties [35].…”