Precision synthesis of 3-substituted urushiol analogues and the realization of their urushiol-like performance

Abstract

Urushiol is a resource-limited natural coating material with diverse applications; however, the synthesis of urushiol analogues and the realization of their urushiol-like performance remain challenging. Herein, four urushiol analogues, namely, 3-((4-alkenoylpiperazin-1-yl)methyl)catechols with the precise 3-substitution pattern on a catechol as that found in urushiol were synthesized by employing the Mannich reaction of catechol with formaldehyde and N-Boc-piperazine as the key step in a two-step route. By using optimization, the advantages of convenience in operation, cost-effectiveness, and scalability could be obtained. The electropolymerization of these analogues on copper was found to be practical due to their higher aerobic stability than urushiol, affording robust coatings with desirable hardness, adhesion strength, hydrophobicity, and thermal stability. Furthermore, the coatings exhibited effective corrosion protection on copper with initial anticorrosion efficiency up to 99.9% and comparatively higher efficiency (more than 97%) after 4 weeks of immersion in 3.5 wt% NaCl solution. The evidence from the electrochemical and infrared spectroscopic characterization data revealed that the electropolymerization process mechanically involved the free radical coupling of phenoxyl radicals to themselves and to the C]C bonds in the side chain, forming a robust crosslinking coating. This work paves a way for the synthesis of high-performance urushiol analogues with potential applications as metal protection materials.Scheme 1 Composition of natural urushiol, structures of synthesized urushiol and urushiol analogues, and synthesis route for urushiol analogues used in this work.This journal is

Synthesis of 4-substituted catechols with side-chains of different CC bond number as urushiol analogues and their anticorrosion performance

“…Furthermore, these coatings were estimated to have corrosion rates ranging from 10 −4 to 10 −5 mm per year, considerably lower than that of bare copper. 16 Calculation of the i corr and CR values of CPA0–3, CPAm and urushiol coatings achieved excellent IE values ranging from 99.85% to 99.99%. The CPA1 and CPA2 coatings exhibited an anticorrosion performance similar to that of natural urushiol.…”

“…The results of cyclic voltammetry and ATR-FTIR combined with the possible mechanisms of urushiol according to different methods 16,21,22 suggested that the electro-polymerisation of the analogues was an electrochemically initiated radical polymerisation process on the copper surface ( Fig. 4b ).…”

“… 27 Notably, the long-term corrosion inhibition effects of these coatings were comparable to those of a recently reported urushiol or lacquer coating 26,28 but inferior to those of urushiol analogue coatings with a 3-substituted structure. 16 Therefore, the substitution position on the catechol not only affected the adhesion capability but also the anticorrosion performance of the urushiol analogues.…”

“…A previous study synthesised 3-substituted catechol at a medium yield via a two-step procedure, namely, Mannich reaction of catechol with formaldehyde and N -Boc-piperazine and deprotection, and amidation with various fatty acids. 16 In the present work, we directly introduced 4-substituted catechol groups and further functionalised amine groups through the reductive amination reaction of 3,4-dihydroxybenzaldehyde and N -Boc-piperazine. Subsequently, we synthesised four 4-substituted catechols with different side chain saturations as urushiol analogues through deprotection and amidation reactions with different unsaturated fatty acids ( Scheme 1 ).…”

PAA‐PU Janus Hydrogels Stabilized by Janus Particles and its Interfacial Performance During Hemostatic Processing

“…[21] Urushiol is the main component of Chinese lacquer applied as early as 6500 years ago, which is a natural product secreted from lacquer tree. [22,23] The endogenous activation of negative charges, the covalent bonding between phenolic hydroxyl groups and tissue, and the hydrophobic barrier of entanglement alkyl chains are play roles synergistically during coagulation cascade. Inspired by the adhesive behavior of mussels, Chen et al [21] synthesized urushiol-functionalized mesoporous silica nanoparticles (MSN@U) used as a hemostatic dressing for the first time.…”