Investigation into thiol-(meth)acrylate Michael addition reactions using amine and phosphine catalysts

Abstract

This work describes a study into thiol-ene based Michael addition reactions. Different catalysts, primary and tertiary amines and phosphines, were investigated for the reaction of a range of thiols with dimers and oligomers of some (meth)acrylates. Primary and tertiary amines are efficient catalysts for the thiol-ene reaction, although these catalysts require several hours to reach high conversion. Moreover, the phosphine catalysts, dimethylphenylphosphine (DMPP) and tris-(2carboxyethyl)phosphine (TCEP), were investigated in detail. DMPP is an efficacious catalyst yielding complete conversion in few minutes under optimized conditions. Importantly, the concentration of DMPP should be kept at catalytic levels to avoid the formation of by-products, originating from the addition of DMPP to the vinyl group. Furthermore, TCEP is an efficient catalyst for thiol-ene reactions in aqueous media when the pH of the medium is higher than 8.0 since at acidic pH the formation of by-products is observed.Scheme 1 Proposed mechanism for the nucleophile mediated hydrothiolation of an acrylic carbon-carbon bond under phosphine catalysis.

Living Radical Polymerization by the RAFT Process – A Third Update

“…A detailed study of the thiol-ene based Michael addition reactions has been reported [612] in which various catalysts, primary and tertiary amines, and phosphines, were investigated for the reaction of thiols with dimeric and oligomeric (meth) acrylate macromonomers. While primary and tertiary amines were effective catalysts for the thiol-ene reaction, several hours were required to reach high conversions.…”

Synthesis and functionalization of dextran-based single-chain nanoparticles in aqueous media

“…22 Using highly polar solvents such as water and under controlled pH, thiols can be used as Michael donors in additions which proceed with high yields and selectivity in mild and clean conditions. [23][24][25] SCPNs resembling disordered proteins were recently prepared by Pomposo et al through classic Michael addition between polymeric precursors The degree of substitution of DXT-MA (DS, MA groups per repeating unit) was around 52%, which is high enough to allow for both intrachain collapse and further functionalization of DXT-SCPN and low enough to maintain water dispersibility. As an example of functionalization, we incorporated carboxylic groups into DXT-SCPN by reaction with mercaptopropionic acid (MPA).…”

“…At different time points (1,3,24,48, 72 and 144 h) samples were withdrawn and the amount of radioactivity was measured. The 67Ga-radiolabelled SCPNs were filtered, washed twice with ultrapure water, and the amount of radioactivity in the filter and the filtrate/washings was measured.…”

Well‐defined poly(oxazoline)‐b‐poly(acrylate) amphiphilic copolymers: From synthesis by polymer–polymer coupling to self‐organization in water

“…[9][10][11] One of the great advantages of this concept was for example the possibility to combine homopolymers preliminary prepared by various living polymerization techniques, such as ringopening polymerization (ROP), ring-opening metathesis polymerization (ROMP), cationic polymerization, nitroxide-mediated radical polymerization (NMP), atom transfer radical polymerization (ATRP), and reversible addition fragmentation chain transfer polymerization (RAFT). Thus, various orthogonal and efficient coupling reactions such as thiol-ene or thiol-ene based Michael addition reactions, [12][13] and Diels-Alder reactions 14 were successfully carried out. Additionally, Huisgen's cycloaddition catalyzed by copper (CuAAC) was investigated to produce block copolymers but only few examples of CuAAC polymer-polymer coupling dealt with the synthesis of amphiphilic copolymers.…”