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Cited by 50Asymmetric Synthesis and Catalysisbiodegradable polymer synthesis and propertiesOrganometallic Complex Synthesis and Catalysis

Exploring Steric Effects in Diastereoselective Synthesis of Chiral Aminophenolate Zinc Complexes and Stereoselective Ring-Opening Polymerization of rac-Lactide

Wang, Haobing, Yang, Yang, Ma, Haiyan·2016·Inorganic Chemistry
DOI 10.1021/acs.inorgchem.6b00378
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Abstract

A series of tridentate chiral aminophenol proligands and corresponding zinc complexes, LZnX (L = (S)-2-{[(1-R(4)-2-pyrrolidinyl)CH2N(R(3))-]CH2}-6-R(1)-4-R(2)-C6H2O, X = N(SiMe3)2, R(3) = (n)Bu, R(4) = Bn: R(1) = R(2) = Cl (1), R(1) = R(2) = Me (2), R(1) = R(2) = (t)Bu (3); X = N(SiMe3)2, R(1) = trityl, R(2) = Me: R(3) = n-octyl, R(4) = Bn (4), R(3) = Bn, R(4) = Bn (5), R(3) = (n)Bu, R(4) = naphthalen-1-ylmethyl (6), R(3) = (n)Bu, R(4) = (i)Pr (7); R(1) = R(2) = cumyl, R(3) = Et, R(4) = Bn: X = N(SiMe3)2 (8), X = O(t)Bu (9), X = Et (10), X = Cl (11)), have been synthesized. Complexes 4, 6, and 11 were obtained as enantiopure products (4 and 6 as enantiopure a; 11 as enantiopure b), while complexes 1-3, 5, and 7-10 as a pair of diastereomers, but in different ratios, which have been proved by X-ray diffraction and NMR spectroscopic studies. When exposed to the ring-opening polymerization of rac-lactide, most of these complexes can effectively produce PLAs with narrow polydispersities, desirable molecular weights, and moderate to high isotacticities. The structure-selectivity relationships, including the relationships of structure-synthesis diastereoselectivity and structure-polymerization stereoselectivity, have been further investigated. Consistent trends of diastereoselectivity and stereoselectivity are observed with the variations of the R(1) group at the ortho-position of the phenolate ring and the R(3) group in the pyrrolidinyl moiety. The decrease of the steric bulkiness of the R(4) group on the central amine has less influence on the diastereoselectivity, but leads to considerable loss of the stereoselectivity, whereas the decrease of the steric bulkiness of the X group results in a reverse of the diastereoselectivity, but shows no influence on the stereoselectivity. There is probably no direct relationship between the diastereoselectivity in complex synthesis and the stereoselectivity of the complex toward the ROP of rac-LA. The stereocontrol of these complexes might largely rely on the substituents in the ligand framework rather than their diastereomer ratios.

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  • Other metal catalysts such as zirconium complexes with bispyrrolidine-salan ligand and zinc complexes with chiral or achiral auxiliary ligands have also been used to generate iso-enriched stereoblock PLAs from rac-LA.

    “Other metal catalysts such as zirconium complexes with bispyrrolidine-salan ligand 312 and zinc complexes with chiral or achiral auxiliary ligands [313][314][315][316] (Figure 7) have also been used to generate iso-enriched stereoblock PLAs from rac-LA.”

    From Catalysis as an Enabling Science for Sustainable Polymers (2018) · cites this paper as [314]

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Authors
Wang, H., Yang, Y., & Ma, H.
Affiliations
East China University of Science and Technology (CN)
Corresponding author
Ma, Haiyan
ORCID
Venue
Inorganic Chemistry
Publisher
American Chemical Society (ACS)
Published
2016-07-20
Volume
55
Issue
15
Pages
7356-7372
ISSN
  • 0020-1669 (ISSN-L)
  • 1520-510X
DOI
10.1021/acs.inorgchem.6b00378
OpenAlex
W2502305139
Cited by
50
References
127
Citations by year
2026: 3 · 2025: 2 · 2024: 1 · 2023: 2 · 2022: 3 · 2021: 5 · 2020: 2 · 2019: 8 · 2018: 7 · 2017: 17
FWCI
4.90
Type
journal article
Language
en
Open access
closed
Locations
  • Inorganic Chemistry (publishedVersion)
  • PubMed (publishedVersion)
Funders
  • Ministry of Education of the People's Republic of China (WD1113011)
  • National Natural Science Foundation of China (21074032, 21474028)
Topics
  • Physical Sciences › Chemistry › Organic Chemistry › Asymmetric Synthesis and Catalysis
  • Physical Sciences › Materials Science › Biomaterials › biodegradable polymer synthesis and properties
  • Physical Sciences › Chemistry › Organic Chemistry › Organometallic Complex Synthesis and Catalysis
Keywords
steric effects, zinc complexes, diastereoselective synthesis, ring-opening polymerization, rac-lactide, polylactic acid, stereoselectivity, structure-selectivity relationship, isotacticity, polydispersity

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