Oxidative cross-coupling of pyridine N-oxides and ethers between C(sp²)–H/C(sp³)–H bonds under transition-metal-free conditions

Abstract

A novel and efficient method based on the cross-coupling reactions of pyridine N-oxides with ethers between C(sp(2))-H/C(sp(3))-H bonds in the presence of TBHP was developed. The strategy provides an alternative approach to the pyridine moiety under transition-metal-free conditions.

Synthesis of Alkyl‐Substituted Pyrazine N‐Oxides by Transition‐Metal‐Free Oxidative Cross‐Coupling Reactions

“…By employing these results and previous reports, we proposed a plausible reaction mechanism (Scheme ). In the presence of tert ‐butyl hydroperoxide, 1,4‐dioxane ( 2 a ) was converted into the corresponding free alkyl radical A along with the release of t BuOH.…”

“…Inspired by reported results, we evaluated the addition of various bases to further improve the yield of this transformation (Table , entries 6–10). However, none of the screened bases improved the outcome.…”

Cross-dehydrogenative coupling and oxidative-amination reactions of ethers and alcohols with aromatics and heteroaromatics

“…In 2015, a metal-free Minisci-type reaction was reported. 45 The precedent for this is a 2009 report on the alkylation of pyridine N-oxides with cycloalkanes and a solitary example of alkylation with 1,4-dioxane. 46 In the earlier work, 46 the reaction of pyridine-N-oxide with 1,4-dioxane and ( t -BuO) 2 at 135 °C gave a 2.2 : 1 mixture of 2,6-dialkylated and 2,4,6-trialkylated pyridine-N-oxide in 61% yield ( Scheme 28 ).…”

Copper‐Catalyzed Deoxygenative C‐2 Amination of Quinoline N‐Oxides

“…Considering the advantages in atomic and step economy in synthetic chemistry, developing a new reduction method without additional reagent is practical. Based on our previous work, we herein disclose an unprecedented reaction between quinoline N ‐oxides and O ‐benzoylhydroxylamines in the presence of CuCl as catalyst in 1,2‐dichloroethane (DCE), affording 2‐aminoquinolines as products in good yields. It should be noted that DCE as solvent is also served as reducing agent to cleave the N–O bond without additional reductant needed in the reaction …”