- Preparation of stereoregular isotactic poly(mandelic acid) through organocatalytic ring-opening polymerization of a cyclic O-carboxyanhydride
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Poly(mandelic acid) (PMA) is an aryl analogue of poly(lactic acid) (PLA) and a biodegradable analogue of polystyrene. The preparation of stereoregular PMA was realized using a pyridine/mandelic acid adduct (Py·MA) as an organocatalyst for the ring-opening polymerization (ROP) of the cyclic O-carboxyanhydride (manOCA). Polymers with a narrow polydispersity index and excellent molecular-weight control were prepared at ambient temperature. These highly isotactic chiral polymers exhibit an enhancement of the glasstransition temperature (Tg) of 15°C compared to the racemic polymer, suggesting potential future application as highperformance commodity and biomedical materials.
- Buchard, Antoine,Carbery, David R.,Davidson, Matthew G.,Ivanova, Petya K.,Jeffery, Ben J.,Kociok-K?hn, Gabriele I.,Lowe, John P.
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- Synergetic Organocatalysis for Eliminating Epimerization in Ring-Opening Polymerizations Enables Synthesis of Stereoregular Isotactic Polyester
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Ring-opening polymerization of O-carboxyanhydrides (OCAs) can furnish polyesters with a diversity of functional groups that are traditionally hard to harvest by polymerization of lactones. Typical ring-opening catalysts are subject to unavoidable racemization of most OCA monomers, which hampers the synthesis of highly isotactic crystalline polymers. Here, we describe an effective bifunctional single-molecule organocatalysis for selective ring-opening polymerization of OCAs without epimerization. The close vicinity of both activating groups in the same molecule engenders an amplified synergetic effect and thus allows for the use of mild bases, thereby leading to minimal epimerization for polymerization. Ring-opening polymerization of manOCA monomer (OCA from mandelic acid) mediated by the bifunctional single-molecule organocatalyst yields highly isotactic poly(mandelic acid) (PMA) with controlled molecular weights (up to 19.8 kg mol-1). Mixing of the two enantiomers of PMA generates the first example of a crystalline stereocomplex in this area, which displayed distinct Tm values around 150 °C. Remarkably, the bifunctional catalysts are moisture-stable, recyclable, and easy to use, allowing sustainable and scalable synthesis of a stereoregular functional polyester.
- Tao, Youhua,Li, Maosheng,Tao, Yue,Tang, Jiadong,Wang, Yanchao,Zhang, Xiaoyong,Wang, Xianhong
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supporting information
p. 281 - 289
(2019/01/04)
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- Synthesis of mirabegron intermediate (R)-2-hydroxy-N-(4-nitrophenyl ethyl)-2-phenylacetamide
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The invention discloses synthesis of mirabegron intermediate (R)-2-hydroxy-N-(4-nitrophenyl ethyl)-2-phenylacetamide. The synthesis method comprises the following steps: performing esterification reaction on R-mandelic acid and triphosgene in a solvent under the existence of alkali to generate a lactide intermediate I; and performing acylation reaction on the intermediate I and 4-nitrophenylethylamine in a solvent to obtain a target product. The synthesis method avoids use of EDCI and HOBt with high price, has the advantages of easily available raw materials, low cost, simplicity in operationand few impurities, and is suitable for industrialized production.
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Paragraph 0026-0027; 0030; 0033
(2018/11/22)
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