Access to Densely Functionalized Chalcone Derivatives with a 2-Pyridone Subunit via Pd/Cu-Catalyzed Oxidative Furan–Yne Cyclization of N-(2-Furanylmethyl) Alkynamides under Air

Abstract

A protocol for synthesis of chalcone derivatives with a 2-pyridone subunit from N-(2-furanylmethyl) alkynamides is reported. This synthesis involves Pd/Cu-catalyzed oxidative furan-yne cyclization at room temperature in air and may proceed via nucleopalladation of the alkyne to form a vinylpalladium intermediate, with a furan ring acting as the nucleophile.

Synthesis of Highly Conjugated Functionalized 2-Pyridones by Palladium-Catalyzed Aerobic Oxidative Dicarbonation Reactions of N-(Furan-2-ylmethyl) Alkyne Amides and Alkenes as Coupling Partners

“…On the basis of the above-described results and previously reported results for Pd-catalyzed difunctionalization of alkynes, − a plausible route for this transformation is illustrated in Scheme . The reaction is initiated by coordination of Pd­(II) with the triple bond of alkyne 1 to afford π-complex I .…”

“…N -(Furan-2-ylmethyl) alkyne amides 1 were known compounds and synthesized according to procedures previously reported in the literature. Analytical data of 1a – 1z was available in the previously reported literature …”

“…Recently, we were the first to report that intramolecular nucleopalladation reactions of alkynes with electron-rich furan rings as nucleophiles are accompanied by opening of the furan ring to afford 3-bromo-2pyridones under extremely mild conditions. 18 We proposed that the structurally complex (2-pyridone-3-yl)palladium intermediate B is generated during this reaction.…”

Gold‐Catalyzed Post‐Ugi Cascade Transformation for the Synthesis of 2‐Pyridones

“…For example, gold‐catalyzed furan–alkyne cyclization/ring‐opening process converting furans into α,β‐unsaturated carbonyl compounds has been advanced by the group of Liu. In addition, during preparation of this work, Jiang, Yin and co‐workers reported a similar approach towards halogenated 2‐pyridones by Pd‐catalyzed furan–alkyne cyclization followed by furan ring‐opening and halogen incorporation (Scheme d) …”

Direct Access to 9-Chloro-1H-benzo[b]furo[3,4-e]azepin-1-ones via Palladium(II)-Catalyzed Intramolecular syn-Oxypalladation/Olefin Insertion/sp2-C–H Bond Activation Cascade

“…Inter- and intramolecular nucleopalladation of alkynes and successive cascade reactions via σ-vinylpalladium intermediates remain excellent strategies to access various structurally diverse molecules in a single synthetic operation (Scheme ). The in situ generated σ-vinylpalladium intermediates could be captured by carbon monoxide, allylic alcohols, halides, esters, allenes, α,β-unsaturated carbonyl compounds, norbornene, styrene, unactivated alkenes, nitriles, and isonitriles to obtain complex compounds . Among the various nucleopalladation reactions, oxypalladation-initiated cascade reactions are particularly important as these reactions lead to a variety of biologically significant compounds including oxygen heterocycles. , …”