Organocatalyzed Aerobic Oxidation of Aldehydes to Acids

Abstract

The first example organocatalyzed aerobic oxidation of aldehydes to carboxylic acids in both organic solvent and water under mild conditions is developed. As low as 5 mol % N-hydroxyphthalimide was used as the organocatalyst, and molecular O 2 was used as the sole oxidant. No transition metals or hazardous oxidants or cocatalysts were involved. A wide range of carboxylic acids bearing diverse functional groups were obtained from aldehydes, even from alcohols, in high yields.

Mechanisms of Csp2–H functionalization of aldehydes with triplet O2 catalyzed by NHPI: A density functional theory investigation

“…According to Dai et al, [ 12 ] with the assistance of N ‐hydroxyphthalimide (NHPI), reactant cyclohexanecarbaldehyde (R1) would react with triplet O 2 to yield cyclohexanecarboxylic acid (P1) in the solvent of CH 3 CN at 30°C in Scheme 2, respectively. Firstly, NHPI, as the catalyst, should go through an activation process to generate radicals, then R1 has two paths to get intermediates IM2, which would continue to react with O 2 ; the obtained intermediate IM3 s should have an intermolecular H‐shift reaction via two possible paths; finally, an SN2 happened to IM4 and IM2 to yield the product P1; meanwhile, the IM5 would become P1 via a H‐shift reaction.…”

“…Inspired by this, Kang and his coworkers employed NHPI and O 2 as the oxidants to convert aldehydes to carboxylic acids at the normal pressure and mild conditions in the solvent of CH 3 CN, which could achieve the metal‐free and environment friendly. [ 12 ] To investigate the detailed mechanisms, theoretical studies have been carried out in the following part.…”

Free‐radical Initialized Cyclization of 2‐(3‐Arylpropioloyl)benzaldehydes with Toluene Derivatives: Access to Benzylated 1,4‐Naphthoquinones via Copper‐Catalyzed Cascade Reaction

“…Here, the aldehyde group functioned as an acceptor for the addition of carbon centered radicals (Scheme 1c). However, this reaction type may encounter some challenges, including the following general concepts: 1) The aldehyde group [17] and benzyl radicals [18] are generally too reactive and frequently over‐oxidized; 2) the internal alkyne is often inert and difficult to react with benzyl radicals. By taking advantage of suitable peroxides and a copper catalyst, we successfully synthesized benzylated 1,4‐naphthoquinones from 2‐(3‐arylpropioloyl) benzaldehydes and toluene derivatives.…”

Air‐Tolerant Reversible Complexation Mediated Polymerization (RCMP) Using Aldehyde

“…reported the first metal‐free catalytic oxidation of aldehydes to carboxylic acids under O 2 , using N ‐hydroxyphthalimide (NHPI ( Figure )) as an organic catalyst ( Scheme a). [ 54 ]…”