Synthesis of <i>N</i>,<i>O</i>‑Spiroacetals and α‑Arylfurans via Pd-Catalyzed Aerobic Oxidative 2,5-Aminoarylation and α‑Arylation of <i>N</i>‑[3-(2-Furanyl)propyl]‑<i>p</i>‑toluenesulfonamides with Boronic Acids

Unsaturated <i>N</i>,<i>O</i>-spiroacetals and α-arylfurans were synthesized via palladium-catalyzed aerobic oxidative coupling reactions between <i>N</i>-[3-(2-furanyl)­propyl]-<i>p</i>-toluene­sulfonamides and boronic acids, with KF and KOAc as the respective additives. These reactions involve an unprecedented dearomatizing 2,5-aminoarylation and a direct α-arylation of furan rings, respectively, with O₂ as the terminal oxidant

Photoinduced Pd-Catalyzed Dearomative 2,5-Difunctionalizition of Furans via Cascade C–C/C–O Bond Formation

We report an efficient and mild approach for radical dearomatization via photoinduced palladium-catalyzed reaction of three components (i.e., furans, alcohols, and bromoalkanes). In this strategy, various functionalized spiro-heterocycles were prepared from furans in one step via cascade C–C/C–O bond formation under redox neutral conditions

Regioselective and Stereoselective Pd-Catalyzed Intramolecular Arylation of Furans: Access to Spirooxindoles and 5<i>H</i>‑Furo[2,3‑<i>c</i>]quinolin-4-ones

Herein, we report regio- and stereoselective intramolecular direct arylations of <i>N</i>-(2-bromophenyl)-2-furancarboxamides <b>1</b> to produce spirooxindoles <b>2</b> and 5<i>H</i>-furo­[2,3-<i>c</i>]­quinolin-4-ones <b>3</b> under different reaction conditions. Specifically, in the presence of Pd­(PPh₃)₄ as a catalyst, PPh₃ as a ligand, and K₂CO₃ as a base, substrates <b>1</b> underwent intramolecular α-arylation, possibly via a Heck insertion pathway, to provide <b>2</b>, with the <i>Z</i>-isomer being favored. When the base was <i>t</i>-BuOLi and R^<b>1</b> was an aryl group, the reaction favored <i>E</i>-<b>2</b>, possibly via an electrophilic palladation pathway. In contrast, in the presence of PdCl₂ as a catalyst, (<i>o</i>-OMePh)₃P as a ligand, and PivOH as an additive, substrates <b>1</b> underwent intramolecular β-arylation to provide <b>3</b>, possibly via a concerted metalation–deprotonation process

Cu(II)-Promoted Transformations of α-Thienylcarbinols into Spirothienooxindoles: Regioselective Halogenation of Dienyl Sulfethers Containing Electron-Rich Aryl Rings

Under the promotion of Cu­(II) salts, the α-thienylcarbinols with an <i>N</i>-phenyl carbonyl group at the other α-position are converted into three different ranges of spirothienooxindoles involving dearomatizing Friedel–Crafts reaction. In addition, the unprecedented regioselective CuX₂-mediated C–H functionalization/halogenation of dienyl sulfether containing electron-rich aryl rings is presented

Synthesis of Spiro-lactams and Polysubstituted Pyrroles via Ceric Ammonium Nitrate-Mediated Oxidative Cyclization of <i>N</i>‑Furan-2-ylmethyl‑β<i>-</i>Enaminones

Spiro-lactams and polysubstituted pyrroles were synthesized by reactions of furfurylamines with ynones followed by oxidation. Specifically, the protocol involved in situ generation of <i>N</i>-furan-2-ylmethyl-β-enaminones and their subsequent oxidation by ceric ammonium nitrate (6 equiv for spiro-lactam formation, 3 equiv for pyrrole formation). This useful dearomatizing oxidation, which likely proceeds via a free-radical pathway, can be expected to extend the synthetic applications of furan and pyrrole derivatives

Synthesis of Spiro-lactams and Polysubstituted Pyrroles via Ceric Ammonium Nitrate-Mediated Oxidative Cyclization of <i>N</i>‑Furan-2-ylmethyl‑β<i>-</i>Enaminones

Spiro-lactams and polysubstituted pyrroles were synthesized by reactions of furfurylamines with ynones followed by oxidation. Specifically, the protocol involved in situ generation of <i>N</i>-furan-2-ylmethyl-β-enaminones and their subsequent oxidation by ceric ammonium nitrate (6 equiv for spiro-lactam formation, 3 equiv for pyrrole formation). This useful dearomatizing oxidation, which likely proceeds via a free-radical pathway, can be expected to extend the synthetic applications of furan and pyrrole derivatives

2,5-Oxyarylation of Furans: Synthesis of Spiroacetals via Palladium-Catalyzed Aerobic Oxidative Coupling of Boronic Acids with α‑Hydroxyalkylfurans

A protocol for the 2,5-oxyarylation of furan rings via Pd-catalyzed aerobic oxidative coupling of boronic acids with α-hydroxyalkylfurans is reported. This protocol provides rapid, green access to diverse biologically interesting and synthetically useful unsaturated spiroacetals from sustainable furan derivatives

Diastereospecific and Enantioselective Access to Dispirooxindoles from Furfurylcyclobutanols by Means of a Pd-Catalyzed Arylative Dearomatization/Ring Expansion Cascade

We report a Pd-catalyzed arylative dearomatization/ring expansion cascade of furfuryl­cyclo­butanols that involves a spiro π-allyl palladium intermediate and affords structurally novel dispirooxindoles containing two quaternary carbon centers in good yields with high step economy, diastereospecificity, and enantioselectivity

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

A protocol for synthesis of chalcone derivatives with a 2-pyridone subunit from <i>N</i>-(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

Diastereospecific and Enantioselective Access to Dispirooxindoles from Furfurylcyclobutanols by Means of a Pd-Catalyzed Arylative Dearomatization/Ring Expansion Cascade

We report a Pd-catalyzed arylative dearomatization/ring expansion cascade of furfuryl­cyclo­butanols that involves a spiro π-allyl palladium intermediate and affords structurally novel dispirooxindoles containing two quaternary carbon centers in good yields with high step economy, diastereospecificity, and enantioselectivity