Mechanistic investigations on Pinnick oxidation: a density functional theory study

Abstract

A computational study on Pinnick oxidation of aldehydes into carboxylic acids using density functional theory (DFT) calculations has been evaluated with the (SMD)-M06-2X/aug-pVDZ level of theory, leading to an important understanding of the reaction mechanism that agrees with the experimental observations and explaining the substantial role of acid in driving the reaction. The DFT results elucidated that the first reaction step (FRS) proceeds in a manner where chlorous acid reacts with the aldehyde group through a distorted six-membered ring transition state to give a hydroxyallyl chlorite intermediate that undergoes a pericyclic fragmentation to release the carboxylic acid as a second reaction step (SRS). 1 H NMR experiments and simulations showed that hydrogen bonding between carbonyl and t -butanol is unlikely to occur. Additionally, it was found that the FRS is a rate-determining and thermoneutral step, whereas SRS is highly exergonic with a low energetic barrier due to the Cl(III) → Cl(II) reduction. Frontier molecular orbital analysis, intrinsic reaction coordinate, molecular dynamics and distortion/interaction analysis further supported the proposed mechanism.

Access and Modulation of Substituted Pyrrolo[3,4-c]pyrazole-4,6-(2H,5H)-diones

“…In the next step, treatment of the derivatives 1 and 2 with POCl 3 and DMF in DCE led to 4-formyl-5-chloropyrazoles 3 and 4 in yields of over 85%. A Pinnick oxidation using sodium chlorite under mild acidic conditions afforded the corresponding acids 5 and 6 in good yields [22][23][24]. An amide bond formation with HOBt and EDCI as peptide coupling reagents [25] was performed in the presence of several amines such as methylamine, aniline or PMBNH 2 to afford the expected amides 7-10.…”

[2+3] Amide Cages by Oxidation of [2+3] Imine Cages – Revisiting Molecular Hosts for Highly Efficient Nitrate Binding

“…By switching the acid from NaH 2 PO 4 to acetic acid, keeping H 2 O 2 as scavenger, the isolated yield for Et‐Ph was still in a comparable range (28 %, Entry 3). Since the Pinnick oxidation is a relative slow reaction, [23d,24] for cages with multiple imine bonds it competes with acid mediated imine bond cleavage, [21,22d,25] if performed in aqueous solution (Entries 1–3). Therefore, water‐free conditions were investigated.…”

Chlorinated Byproduct Formation during the Electrochemical Advanced Oxidation Process at Magnéli Phase Ti4O7 Electrodes

“…Organic chlorinated byproducts with masses of 84, 150, and 178 Da were detected in the NaOCl/resorcinol solution (Figures S8 and S9). Structures with masses of 82.5, 150.5, and 178.9 Da were proposed as possible products for the reaction between resorcinol and HOCl/OCl – (Figure S10 and Table S2) and were based on results from the literature. − Products include a chlorinated phenolic compound (mass = 178.9 Da) and chlorinated aliphatic compounds (masses = 150.5 and 82.5 Da). The products for direct reaction between resorcinol and HOCl/OCl – were distinctly different from those for electrochemical oxidation experiments (Figure ), indicating that oxidation of resorcinol in electrochemical experiments was not solely attributed to reactions with HOCl/OCl – .…”