Isothiourea‐based lewis pairs for homopolymerization and copolymerization of 2,2‐dimethyltrimethylene carbonate with ε‐caprolactone and ω‐pentadecalactone

Abstract

In this study, the homopolymerization of 2,2‐dimethyltrimethylene carbonate (DTC) and its copolymerizations with ε‐caprolactone (CL) were carried out in detail using the isothiourea‐based Lewis pairs comprised 2,3,6,7‐tetrahydro‐5H‐thiazolo(3,2‐a)pyrimidine and magnesium halides (MgX2) with benzyl alcohol (BnOH) as the initiator. The copolymerization of DTC and CL via one‐pot addition produced randomly sequenced copolymers. On the other hand, a well‐defined linear poly(ε‐caprolactone)–block–poly(2,2‐dimethyltrimethylene carbonate) (PCL‐b‐PDTC) diblock copolymer was prepared by simple sequential ring‐opening polymerization of CL and DTC. In addition, poly(ω‐pentadecalactone)–block–PDTC diblock copolymer was successfully prepared by the same strategy. Moreover, PDTC–poly(ethylene glycol) (PEG)–PDTC triblock copolymer was synthesized in the presence of PEG 2000. The effects of different polymerization conditions on the polymerization reactions have been systematically discussed. The resulting polymers were characterized by the 1H and 13C NMR spectra, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐ToF MS). The block copolyester structures were confirmed by the 13C NMR spectroscopy and DSC characterizations. These results indicated that the supposed mechanism was a dual catalytic mechanism. The proposed mechanism involved activation of the monomer via coordination to the MgX2, and the initiator alcohol was deprotonated by base. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2349–2355

Mastering Macromolecular Architecture by Controlling Backbiting Kinetics during Anionic Ring-Opening Polymerization

“…However, when the experiment was repeated with the AROP of εCL first, followed by the sequential addition of PDL, entirely random copolymers were formed (Figure 4). These observations are coherent with previous work on block copolymers containing PDL blocks, where the small-ring-sized monomer of enthalpic driving force, such as lactide, 63,67 εCL, 63 or 2,2-dimethyltrimethylene carbonate, 68 for sequential monomer addition is exclusively used as a second block. In contrast, as far as we know, there are no examples of well-defined block copolymers with PDL as the second block, except reports of simultaneous addition to yield tapered block copolymers.…”

Visible-light driven regioselective synthesis, characterization and binding studies of 2-aroyl-3-methyl-6,7-dihydro-5H-thiazolo[3,2-a]pyrimidines with DNA and BSA using biophysical and computational techniques

“…It is well recognized that the thiazolo[3,2- a ]pyrimidine; a fused heterocyclic system consisting of six-membered pyrimidine and five-membered thiazole rings with bridgehead nitrogen atom is a privileged motif found in numerous natural products and various synthetic compounds. In the recent times, it has emerged as a potential synthetic area in heterocyclic synthesis due to its widespread applications among as acetylcholinesterase inhibitor 1 , calcium antagonist 2 , cytotoxic agent 3 , antitubercular, CDC25 phosphatase inhibitor 4 , antidepressant 5 as well as in polymerization reactions as co-polymer 6 – 8 . Although short of literature, the synthesis of thiazolo[3,2- a ]pyrimidine nucleus has been reported by the sodium acetate catalyzed reaction of tetrahydropyrimidine-5( H )-2-thione with α-halo carbonyl compounds 1 , 5 , 9 in acetic acid reflux, 1,1,1,3,4,4,5,5,5-nonafluoro-2-(trifluoromethyl)pent-2-ene 10 in triethylamine catalyzed acetonitrile reflux and by the reaction of aromatic aldehydes with 2-aminothiazole and malononitrile/diethyl malonate/ethyl 2-cyanoacetate in piperidine catalyzed ethanolic reflux 11 , 12 .…”