Facile, Efficient Routes to Diverse Protected Thiols and to Their Deprotection and Addition to Create Functional Polymers by Thiol−Ene Coupling

Abstract

Carbazole, dinitrobenzoate, phenol, pyridine, and 4-cyano-4′-alkoxybiphenyl side groups were grafted onto pendant vinyl groups of polybutadiene (PB) by thiol-ene addition to yield functional polymer of polydispersity equal to that of the precursor material. Synthesis protocols that are clean (>90% conversion to desired product) and scalable were developed to incorporate a protected thiol group into functional precursors. The resulting acetyl or benzoyl thioesters are suitable for long-term storage, and are conveniently deprotected and added to polymer in a matter of hours in a straightforward procedure that does not require isolation of the thiol intermediate. Alternatively, PB functionalization could be achieved with equal success by reaction with β-mercaptoethanol (BME), and subsequent esterification of the incorporated hydroxyl groups with a suitable acyl halide. The chemistry described can potentially be applied to add any side group onto any polymer, copolymer, or block copolymer displaying pendant vinyl groups.

Thiol‐Ene Radical Addition of L‐Cysteine Derivatives to Low Molecular Weight Polybutadiene

“…The structure reported in Figure 1, including five-membered cyclic units, has been inferred by previous studies on the thiol-ene reactions on PBLs; in these studies, the formation of 5-and 6-membered cycles was observed. [56,62] As discussed by Ameri David and Kornfield, [62] the 1 H NMR attribution of aliphatic protons bonded to the carbon next to the sulfur atom (in Figure 1, protons number 5 and 6) is very difficult, owing to the presence of overlapping peaks (especially proton number 4). A confirmation of the presence of five-membered cyclic units in PBNCys100, instead, can arise from the evaluation of the 13 C NMR spectrum: in the [22. .…”

“…The 1 H NMR spectrum of the functionalised sample PBNCys100 showed peaks assigned according to Gonzalez de la Campa and Pham, [23] Schlaad and coworkers [55,56] and Ameri David and Kornfield [62] studies. In Figure 1 we report the spectrum and the structure of the functionalised PBL with complete attribution of observed peaks.…”

Fatty Acid Derived Monomers and Related Polymers Via Thiol‐ene (Click) Additions

“…[19] More recent investigations have shown that quite high molecular weight polythioethers can be obtained in that way, [20] that initiators are not necessary for the reaction to proceed, [21] but radical inhibitors suppress the polymerization for some time. [21] Today, the reaction is used in the sense of a click reaction for the synthesis of dendrimers, [22] the grafting of side-groups to reactive polymers, [23,24] or the synthesis of star polymers. [25] Also in the field of oleochemistry thiol-ene additions are known for a long time.…”

Novel thiol- amine- and amino acid functional xylan derivatives synthesized by thiol–ene reaction

“…Polythiols are difficult to synthesize otherwise due to their reactivity and because free thiol-groups are prone to oxidation by atmospheric oxygen yielding non-soluble crosslinked products. Although the thioester group has been used as a thiol precursor for a long time (Chapman & Owen, 1950) and it has been applied also to polymers, such as cellulose (Schwenker et al, 1962), chitin (Kurita, Yoshino, Nishimura, & Ishii, 1993) and polyethylene glycol (Woghiren, Sharma, & Stein, 1993), this versatile thiol-ene approach has only been reported for the end functionalization of poly(ethylene glycol) (Goessl, Tirelli, & Hubbell, 2004) and grafting of polybutadiene (David & Kornfield, 2008).…”