N‐Heterocyclic Carbenes as Organic Catalysts

Dove, Andrew P.; Pratt, R. H.; Lohmeijer, Bas G. G.; Li, Hongbo; Hagberg, Erik C.; Waymouth, Robert M.; Hedrick, James L.

doi:10.1002/9783527609451.ch12

Cited by 27 publications

(26 citation statements)

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“…The demonstration by Breslow showed that stabilized singlet carbenes derived from thiamine cofactors are nucleophilic catalysts, and the pioneering works of Wanzlick and coworkers on the deprotonation of thiazolium and imidazolium salts, are considered to be the first steps in the use of N‐heterocyclic carbenes (NHCs) as nucleophilic catalysts . The first reported example of NHC catalyzing β‐lactone polymerization was used for the ROP of BL in the presence of the 1,3‐bis‐(2,4,6‐trimethylphenyl)imidazole‐2‐ylidene (IMes) NHC from pyrene‐butanol in THF at 25 °C .…”

Section: Zwitterionic and Anionic Metal‐free Rops Of β‐Lactonesmentioning

confidence: 99%

Organocatalysis applied to the ring‐opening polymerization of β‐lactones: A brief overview

Khalil

Cammas‐Marion

Coulembier

2019

J. Polym. Sci. Part A: Polym. Chem.

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Organocatalysis offers a number of prospects in the polymer community and presents advantages over metal based and bio‐organic methods. The use of organic molecules for performing chemical reactions is not a new concept, and any research into organocatalytic reactions builds on a respected history. Compared to the organocatalysis of large lactones, which began in the early 2000s, the examples presented here will demonstrate that few metal‐free initiating systems had been applied to β‐lactones well before the beginning of the current millennium. These metal‐free initiating systems present indisputable advantages over metal‐based processes. In the following paper, ring‐opening polymerizations (ROPs) of various β‐lactones for the preparation of poly(hydroxyalkanoate)s will be presented, as will the types of mechanisms involved, that is, zwitterionic and anionic, and cationic or supramolecular‐based ROPs. The advantages and drawbacks of the different technics will be discussed in the domain, which, for us, is important in the overall production of bioplastics. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 657–672

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Section: Zwitterionic and Anionic Metal‐free Rops Of β‐Lactonesmentioning

confidence: 99%

Organocatalysis applied to the ring‐opening polymerization of β‐lactones: A brief overview

Khalil

Cammas‐Marion

Coulembier

2019

J. Polym. Sci. Part A: Polym. Chem.

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“…[5] However, the complex chemistry of this system is not yet fully understood, especially considering that rapid decomposition of the Ni NHC catalyst releases free NHC into the reaction media. [11] Because free NHC is highly reactive, [12][13][14][15][16] and is released from the Ni NHC catalyst during AB dehydrogenation, its reactivity should be considered. In addition to the free NHC / Ni NHC catalytic pathway proposed herein, we have also shown that Ni NHC catalysts competitively dehydrogenate AB.…”

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confidence: 99%

The Role of Free N‐Heterocyclic Carbene (NHC) in the Catalytic Dehydrogenation of Ammonia–Borane in the Nickel NHC System

et al. 2009

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“…Unfortunately, all the reported purification processes are generally complex and highly cost 29–33. Very recently, Waymouth and Hedrick's group has reported various organocatalysts such as N‐heterocyclic carbenes (NHC) for the formation of both cyclic and linear biopolymers by zwitterionic ROP 34–39. Unlike metal based catalysts, ROP catalyzed by the NHCs produce “green” cyclic polymers without any metal contamination caused by the trapped catalyst species 34–39.…”

Section: Introductionmentioning

confidence: 99%

Syntheses of cyclic poly(lactones) by zwitterionic ring opening polymerization catalyzed by N‐heterocyclic carbene

Prasad

Zhu

2012

J of Applied Polymer Sci

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Synthesis of cyclic biopolymers from renewable monomers remains a big challenge because of lack of efficient catalysts. The organocatalyst of N‐heterocyclic carbene (NHC), (+)‐1‐methyl‐3‐menthoxymethyl imidazol‐2‐ylidene, is used to prepare cyclic polylactones including poly(ε‐caprolactone) (poly(ε‐CL)), poly(δ‐valearolactone) (poly(δ‐VL)), and poly(ε‐caprolactone‐co‐δ‐valearolactone) (poly(ε‐CL‐co‐δ‐VL)) via zwitterionic ring opening polymerization. The NHC catalyst is founded a highly efficient organic catalyst for the polymerization. The resulting cyclic polymers show a melting temperature (Tm) in a range of 20–60°C, which is dramatically lower than the Tm of cyclic poly(lactide) (Tm = 120–150°C). The resulting copolymer, cyclic poly(ε‐CL‐co‐δ‐VL) owns high molecular weight comparing with corresponding linear poly(ε‐CL‐co‐δ‐VL) produced by other catalysts. The synthesized cyclic homo and copolymers were characterized by 1H‐, 13C‐NMR spectroscopy, gel permeation chromatography, differential scanning calorimetry–thermogravimetric analysis and matrix‐assisted laser desorption ionization‐time of flight mass spectrometry. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

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N‐Heterocyclic Carbenes as Organic Catalysts

Cited by 27 publications

References 0 publications

Organocatalysis applied to the ring‐opening polymerization of β‐lactones: A brief overview

Organocatalysis applied to the ring‐opening polymerization of β‐lactones: A brief overview

The Role of Free N‐Heterocyclic Carbene (NHC) in the Catalytic Dehydrogenation of Ammonia–Borane in the Nickel NHC System

Syntheses of cyclic poly(lactones) by zwitterionic ring opening polymerization catalyzed by N‐heterocyclic carbene

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