Postpolymerization Modification of Poly(dihydropyrimidin-2(1H)-thione)s via the Thiourea–Haloalkane Reaction to Prepare Functional Polymers

Abstract

A highly reactive thiourea-contained polycondensate, poly(dihydropyrimidin-2(1H)-thione) (poly-(DHPMT)) has been facilely synthesized via the Biginelli polycondensation using thiourea and a difunctional compound containing benzaldehyde and β-keto ester groups as monomers. The thiourea moiety in the polymer structure has similar reactivity as the thiourea, thus the poly(DHPMT) is an excellent polymer precusor for preparing new functional polymers through the postpolymerization modification (PPM) strategy. After simple reaction with functional haloalkanes, the parent poly(DHPMT) could be almost completely converted (>99%) to daughter polymers containing alkene or alkyne side groups. Then, the daughter polymers have been further transferred to granddaughter polymers through another PPM via thiol− ene or Cu(I)-catalyzed azide−alkyne cycloaddition (CuAAC) reactions. Besides, when 3-phenylpropargyl chloride was used as the reactant, a bright yellow fluorescent polymer could be simply achieved due to the in situ formed conjugated heterocycle in the polymer structure, further demonstrating the diversity of the functional polymers through PPM. Considering the easily available monomers, simple polycondensation, and the excellent reactivity of the thiourea moiety in the polymer structure, this thiourea-contained Biginilli polycondensate might be a versatile platform for new functional polymer preparation.S ince the middle of the twentieth century, the concept of a macromolecule has been formally accepted, and many strategies have been successfully developed to prepare polymers with designed functions. Among them, postpolymerization modification (PPM) might be one of the most important to prepare new functional polymers by modifying the reactive chain ends or side chains of polymer precursors. 1−5 The history of PPM could actually date back to 1840 when Hancock and Ludersdorf independently reported the first PPM by treating natural rubber with sulfur to produce a tough and elastic material. 6,7 Until now, some large-scale manufactured polymers, such as poly(vinyl alcohol) (PVA), chitosan, some functional resins, etc., are still produced through the PPM strategy. However, traditional modification reactions normally have low efficiency and are easily hampered by the steric hindrance of giant polymer chains, leading to polymers with undefined structure and properties. PPM has therefore been overshadowed by other strategies to synthesize clearly structured polymers. 8−11With the recent development of modern efficient modular reactions, such as the click reactions 12−19 and highly efficient multicomponent reactions (MCRs), 20−34 functional groups can be effectively introduced into the polymer chain once the polymer precursor containing corresponding reactive modules are obtained. 1,35,36 Thus, the PPM strategy has regained attention, and a series of elegant polymers with clear structure have been successfully prepared through this "old" method. 35−39 By now, how to synthesize highly reactive polymer precursors and how to choose e...

Chemoselective Lewis pair polymerization of renewable multivinyl-functionalized γ-butyrolactones

“…Subsequently, all organic layers were combined and dried with sodium sulfate prior to the removal of dichloromethane under reduced pressure to afford γ VMMBL as a liquid (5.16 g, 72% isolated yield). 1 (e) Synthesis of γ-allyl-γ-methyl-α-methylene-γ-butyrolactone (i) Isolation of methyl oxalyl γ-allyl-γ-methyl-γ-butyrolactone sodium salt…”

“…Subsequently, all organic layers were combined and dried with sodium sulfate prior to the removal of dichloromethane under reduced pressure to afford γ AMMBL as a liquid (0.31 g, 73% isolated yield relative to AGVL). 1…”

“…For post-functionalization or processing into advanced functional materials for various applications, polymers are required to bear chemically, thermally or photochemically sensitive functional groups [1][2][3][4][5][6][7][8]. The desired method for the synthesis of such functional polymers is chemoselective polymerization of multi functional monomers by safeguarding one or more of the 2017 The Author(s) Published by the Royal Society.…”

Click and Multicomponent Reactions Work Together for Polymer Chemistry

“…To date there has been a unique example featuring this combination studied by Tao and coworkers. In this report, Biginelli polycondensation using thiourea and difunctional compound with benzaldehyde and β‐keto ester groups was carried out in acetic acid to yield a poly(dihydropyrimidin‐2(1H)‐thione) polycondensate at 100 °C for 50 min ( Scheme ) . Thiourea linkage in the Biginelli ring was deliberately chosen because of its excellent nucleophilic character in substitution reaction with haloalkane.…”

“…Biginelli polycondensation followed by thiol‐ene or CuAAC. Reproduced with permission . Copyright 2018, American Chemical Society.…”