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Mixture of Azolium Tetraphenylborate with Isopropylthioxanthone: A New Class of N‐Heterocyclic Carbene (NHC) Photogenerator for Polyurethane, Polyester, and ROMP Polymers Synthesis
- Source :
- Chemistry-A European Journal, Chemistry-A European Journal, Wiley-VCH Verlag, 2019, 25 (39), pp.9242-9252. ⟨10.1002/chem.201901000⟩
- Publication Year :
- 2019
- Publisher :
- Wiley, 2019.
-
Abstract
- In the search of smarter routes to control the conditions of N-heterocyclic carbene (NHCs) formation, a two-component air-stable NHC photogenerating system is reported. It relies on the irradiation at 365 nm of a mixture of 2-isopropylthioxanthone (ITX) with 1,3-bis(mesityl)imidazoli(ni)um tetraphenylborate. The photoinduced liberation of NHC is evidenced by reaction with a mesitoyl radical to form an NHC-radical adduct detectable by electron spin resonance spectroscopy. The NHC yield can be determined by 1 H NMR spectroscopy through the formation of a soluble and stable NHC-carbodiimide adduct. To deprotonate the azolium salt and liberate the NHC, a mechanism is proposed in which the role of base is played by ITX radical anion formed in situ by a primary photoinduced electron-transfer reaction between electronically excited ITX (oxidant) and BPh4 - (reductant). An NHC yield as high as 70 % is achieved upon starting with a stoichiometric ratio of ITX and azolium salt. Three different photoNHC-mediated polymerizations are described: synthesis of polyurethane and polyester by organocatalyzed step-growth polymerization and ring-opening copolymerization, respectively, and generation of polynorbornene by ring-opening metathesis polymerization using an NHC-coordinated Ru catalyst formed in situ.
- Subjects :
- Isopropylthioxanthone
Tetraphenylborate
010405 organic chemistry
Organic Chemistry
General Chemistry
ROMP
010402 general chemistry
Metathesis
01 natural sciences
Catalysis
0104 chemical sciences
Adduct
chemistry.chemical_compound
[CHIM.POLY]Chemical Sciences/Polymers
chemistry
Polymerization
Polymer chemistry
Copolymer
Carbene
ComputingMilieux_MISCELLANEOUS
Subjects
Details
- ISSN :
- 15213765 and 09476539
- Volume :
- 25
- Database :
- OpenAIRE
- Journal :
- Chemistry – A European Journal
- Accession number :
- edsair.doi.dedup.....0fde18801b327795f4bd5fccb89377f2