Thiol–Ene Click Chemistry

Abstract

Following Sharpless' visionary characterization of several idealized reactions as click reactions, the materials science and synthetic chemistry communities have pursued numerous routes toward the identification and implementation of these click reactions. Herein, we review the radical-mediated thiol-ene reaction as one such click reaction. This reaction has all the desirable features of a click reaction, being highly efficient, simple to execute with no side products and proceeding rapidly to high yield. Further, the thiol-ene reaction is most frequently photoinitiated, particularly for photopolymerizations resulting in highly uniform polymer networks, promoting unique capabilities related to spatial and temporal control of the click reaction. The reaction mechanism and its implementation in various synthetic methodologies, biofunctionalization, surface and polymer modification, and polymerization are all reviewed.

Versatile click alginate hydrogels crosslinked via tetrazine–norbornene chemistry

“…In this work, photoinitated thiolene chemistry between norbornene and cysteine-bearing RGD peptides was employed to rapidly modify click alginate hydrogels to present adhesion ligands on the surface of the gel. This thiol-ene reaction is a powerful light-mediated click reaction that is simple, reproducible, fast, and highly efficient -achieving conversions nearing completion in aqueous media [41]. Although we did not investigate the thiol-ene reaction conversion as a function of hydrogel depth specifically, several recent papers have reported the ability to functionalize the interiors of hydrogels using this method [28,30,42,43].…”

Photocuring and thermal post-curing of a cycloaliphatic epoxide resin with a trithiol and a vinyl epoxy compound

“…where dh/dt is the heat flow released by the sample during the photocuring, integrated up to a time t and Dh calc has been estimated considering a heat of reaction of 80 kJ ee -1 for the polymerization of the epoxy resin a heat of reaction of 43.9 kJ mol -1 for the addition of the thiol group across the double bond of the vinyl compound [9]. In the photocuring studied by FTIR, a ep represents the conversion of the epoxy groups.…”

“…There are several applications of the click reactions, like high performance of protective polymer networks, protective coatings, films and optical, biomedical and bioorganic fields [9]. Thiol-ene reaction (see Scheme 1) is a kind of versatile click reaction widely used for synthetic purposes but also in thermosetting formulations having applications such as dental restorative materials [10] or reinforced composites with structural applications [11].…”

Purification of Peptides in High-Complexity Arrays

“…Difficulties in the coupling amino acids to the SMCC introduces a maleimide function which allows for the covalent immobilization of peptides across a cysteine according to the well known principle of "click chemistry" (see Figure 39). [157][158] Thus, pre-synthesized peptides could be coupled to the surfaces under ambient conditions. Spotting of carboxyl-activated peptides from anhydrous solutions would have required different equipment which was not available in the present work.…”