Cu(ii)-catalyzed C6-selective C–H thiolation of 2-pyridones using air as the oxidant

Abstract

The Cu(II)-catalyzed and chelate-directed C6-selective C-H thiolation of 2-pyridones with disulfides was developed to provide aryl and alkyl thioethers. This transformation uses a catalytic amount of Cu(OAc) 2 and molecular oxygen in air as an oxidant, no cocatalysts or metallic oxidants are required. The reaction accommodated both electronic and steric factors at the C3-C5 positions of 2-pyridones, which is efficient for the C6 thiolation of a broad range of 2-pyridones with up to 93% yield.

A comprehensive overview of directing groups applied in metal-catalysed C–H functionalisation chemistry

“…Finally, Liu demonstrated the aryl- and alkylthiolation of 2-pyridones with disulfides under Cu/Brønsted acid catalysis ( Scheme 120H ). 734 It is worth mentioning that, although some of these reactions required an air atmosphere, an O 2 atmosphere proved deleterious for the reaction, 728 , 729 , 734 presumably due to sulphur oxidation in the reactants/products.…”

A lesson for site-selective C–H functionalization on 2-pyridones: radical, organometallic, directing group and steric controls

“…Jiang and Liu reported a Cu( ii )-catalysed thiolation with disulfides ( Scheme 26 ). 36 Both diaryl- and dialkyldisulfides participated in the reaction, and the corresponding C6-thiolated pyridones were obtained in good to high yields. Similar to in Scheme 16 , the acidic additives had positive effects on the reaction, with 2-biphenylcarboxylic acid ( o -PBA) proving to be optimal in the C–H thiolation.…”

Rhodium(III)‐Catalyzed C−H Bond Functionalization of 2‐Pyridones with Alkynes: Switchable Alkenylation, Alkenylation/Directing Group Migration and Rollover Annulation

“…In pioneering studies, Hirano and Miura introduced an easily attachable and detachable pyridine‐based directing group (DG) on the nitrogen atom of the 2‐pyridone skeleton to facilitate C6‐selective heteroarylation of 2‐pyridones [7c] . Subsequently, transition‐metal catalyzed directed alkynylation, [6d] alkylation, [7e,h,l,u] annulation, [7f,o] borylation, [7g] arylation, [7h,k,m] thiolation, [7i] allylation, [7j] amidation [7p,q] and alkenylation [7s,t] of 1‐(2‐pyridyl)‐2‐pyridones at the C6 positions have been successfully developed. In general, the pyridyl directing group in these C−H functionalizations remains intact and can be removed from the final products.…”