Rhodium(III)‐Catalyzed Regioselective C−H Annulation and Alkenylation of 2‐Pyridones with Terminal Alkynes

Abstract

Cp*Rh(III)‐catalyzed regioselective C−H annulation and alkenylation of 2‐pyridones with terminal alkynes have been developed. The cationic Cp*Rh(III) catalytic system containing FeCl3 additive enables annulation of 1‐(2‐pyridyl)‐2‐pyridones with terminal alkynes, providing efficient access to 5,7‐diarylated 2‐quinolinones. The reaction pathway can be switched to alkenylation with [Cp*RhCl2]2 as the catalyst, NaOAc as the additive and HOAc as the solvent, affording C6‐alkenylated 1‐(2‐pyridyl)‐2‐pyridones in high yields. These protocols accommodate a wide range of substrates with good functional group compatibility.

Pd(II)-Catalyzed Oxidative Naphthylation of 2-Pyridone through N–H/C–H Activation Using Diarylacetylene as an Uncommon Arylating Agent

“…Therefore, steady progress has been observed in the direct step-economic modifications of 2-pyridone and related scaffolds . In the search for promising structurally diverse 2-pyridone scaffolds, an internal alkyne was considered as a useful coupling component in the direct C–H bond functionalizations of 2-pyridone scaffolds . Since the development of the Satoh–Miura type oxidative annulation of arenes with internal alkynes via twofold C–H bond functionalizations, many elegant strategies have been developed to obtain polyaromatic naphthalene skeletons (Scheme a), especially under palladium-catalyzed conditions .…”

Directing group-assisted selective C–H activation of six-membered N-heterocycles and benzo-fused N-heterocycles

“…The Qian Shi group, in 2022, presented Rh(III)-catalysed regioselective C-H annulation and alkenylation of 2-pyridones 74 with terminal alkynes 93 (Scheme 61). 96 They found that decreasing the temperature of the reaction or the catalyst loading turned out to be detrimental to the reaction. The cationic Cp*Rh(III) catalyst with FeCl 3 as additive gave the annulated product with terminal alkynes.…”

Rhodium-Catalyzed 1,4-Aryl Rearrangement of Sulfur Ylide for the Synthesis of 2-Pyridyl Thioethers

“…We expected to harness the power of the metal carbene and the good nucleophilicity of the thiocarbonyls to generate sulfur ylides in a facile and catalytic fashion and trigger remote group shift behavior. Inspired by the intramolecular nucleophilic aromatic substitution (S N Ar) of the C− Rh bond with a pyridyl moiety during C−H functionalization, 17 we herein present a novel rhodium-catalyzed sulfur-ylide [1,4]aryl rearrangement reaction for the synthesis of pyridyl thioethers with tetrasubstituted carbon stereocenters. In the reaction, a N-substituted thiopyridone reacts with a metal carbene to generate a sulfur ylide that subsequently undergoes novel [1,4]-aryl rearrangement through direct cleavage of the C−N bond and the formation of a C−C bond.…”

“…We propose a plausible mechanism based on the observations described above and literature precedent (Scheme ). , The rhodium­(II) catalyst initially reacts with 2a to generate rhodium carbene species A , which undergoes C–S bond coupling through the addition of 1a to A to form the metal-bound sulfur ylide B . Subsequently, B experiences a cyclization to generate the five-membered intermediate C (pathway a ).…”