Mild addition of carbon nucleophiles to pyridine and quinoline N-oxides under different activation conditions

Three-Component Synthesis of Pyridylacetic Acid Derivatives by Arylation/Decarboxylative Substitution of Meldrum's Acids

A convenient and simple three-component synthesis of substituted pyridylacetic acid derivatives is reported. The approach centers on the dual reactivity of Meldrum's acid derivatives, initially as nucleophiles to perform substitution on activated pyridine-N-oxides, then as electrophiles with a range of nucleophiles to trigger ring-opening and decarboxylation.

Silver-catalyzed direct C-H oxidative carbamoylation of quinolines with oxamic acids

A silver-catalyzed efficient and direct C-H carbamoylation of quinolines with oxamic acids to access carbamoylated quinolines has been developed through oxidative decarboxylation reaction. The reaction proceeds smoothly over a broad range of substrates with excellent functional group tolerance and excellent yields under mild conditions.

Organic dye-photocatalyzed fluoroalkylation of heteroarene-N-oxide derivatives

A direct C_Het–H perfluoroalkylation reaction of heteroaromatic-N-oxides has been achieved. Acid-catalyzed transformation of the perfluoroalkylated-N-oxides leads to 2-(perfluoroalkyl)benzo[f][1,3]oxazepines. De-oxygenation of the perfluoroalkylated heteroaromatic-N-oxides affords a regioselective radical perfluoroalkylation protocol.

A direct metal-free C2–H functionalization of quinoline N-oxides: a highly selective amination and alkylation strategy towards 2-substituted quinolines

An efficient one-pot methodology for C2-selective amination and alkylation of quinoline N-oxides was developed in the presence of diethyl H-phosphonate.

A convergent, umpoled synthesis of 2-(1-amidoalkyl)pyridines

A convenient, one-pot, two-component synthesis of 2-(1-amidoalkyl)pyridines is reported, based upon the substitution of suitably-activated pyridine N-oxides by azlactone nucleophiles, followed by decarboxylative azlactone ring-opening. The synthesis obviates the need for precious metal catalysts to achieve a formal enolate arylation reaction, and constitutes a formally ‘umpoled’ approach to this valuable class of bioactive structures.

Regioselective Metal-Free Cross-Coupling of Quinoline N-Oxides with Boronic Acids

A novel and operationally simple one-step C-H bond functionalization of quinoline N-oxides to 2-substituted quinolines was developed. This approach enables the regioselective functionalization under external oxidant- and metal-free conditions. The developed transformation represents the first application of the Petasis reaction in functionalization of heterocycles.

Selective perfluoro- and polyfluoroarylation of Meldrum's acid

This work describes the facile and mono-selective per- and polyfluoroarylation of Meldrum's acid to generate a versatile synthon for highly fluorinated α-phenyl acetic acid derivatives, which provide straightforward access to fluorinated building blocks. The reaction takes place quickly, and most products were isolated without the need for chromatography. Importantly, this method provides an alternative strategy to access α-arylated Meldrum's acids, which avoids the need for aryl-Pb(IV) salts or diaryliodonium salts. Furthermore, we demonstrate the synthetic versatility and utility of the Meldrum's acid products by subjecting our products to several derivatizations of the Meldrum's acid products as well as photocatalytic hydrodefluorination.

Expedient synthesis of α-(2-azaheteroaryl) acetates via the addition of silyl ketene acetals to azine-N-oxides

A new and expedient synthesis of α-(2-azaheteroaryl) acetates is presented. The reaction proceeds rapidly under mild conditions via the addition of silyl ketene acetals to azine-N-oxides in the presence of the phosphonium salt PyBroP. This procedure affords diverse α-(2-azaheteroaryl) acetates which are highly desirable components/building blocks in molecules of pharmaceutical interest but are traditionally challenging to synthesize via contemporary methods. The reaction optimization and mechanism as well as a novel electronically enhanced PyBroP derivative are described.