Liberation of N-heterocyclic carbenes (NHCs) from thermally labile progenitors: protected NHCs as versatile tools in organo- and polymerization catalysis

2014 ◽  
Vol 4 (8) ◽  
pp. 2466-2479 ◽  
Author(s):  
Stefan Naumann ◽  
Michael R. Buchmeiser
Keyword(s):  
Heterocyclic Carbenes ◽  
Triggered Release ◽  
Polymerization Catalysis ◽  
Catalytically Active ◽  
Thermally Triggered

The thermally triggered release of catalytically active, free NHCs from various heat-sensitive progenitors is discussed.

Thermally triggered release of a pro-osteogenic peptide from a functionalized collagen-based scaffold using thermosensitive liposomes

2014 ◽  
Vol 187 ◽  
pp. 158-166 ◽  
Author(s):  
Adolfo López-Noriega ◽  
Eduardo Ruiz-Hernández ◽  
Elaine Quinlan ◽  
Gert Storm ◽  
Wim E. Hennink ◽  
...  
Keyword(s):  
Triggered Release ◽  
Thermosensitive Liposomes ◽  
Thermally Triggered

Microarrays of over 2000 hydrogels – Identification of substrates for cellular trapping and thermally triggered release

Biomaterials ◽  
2009 ◽  
Vol 30 (31) ◽  
pp. 6193-6201 ◽  
Author(s):  
Rong Zhang ◽  
Albert Liberski ◽  
Rosario Sanchez-Martin ◽  
Mark Bradley
Keyword(s):  
Triggered Release ◽  
Thermally Triggered

scholarly journals Modulating NHC catalysis with fluorine

2013 ◽  
Vol 9 ◽  
pp. 2812-2820 ◽  
Author(s):  
Yannick P Rey ◽  
Ryan Gilmour
Keyword(s):  
Small Molecule ◽  
Heterocyclic Carbenes ◽  
Fluorine Substitution ◽  
X Ray ◽  
Catalytically Active ◽  
Triazolium Salts

Fluorination often confers a range of advantages in modulating the conformation and reactivity of small molecule organocatalysts. By strategically introducing fluorine substituents, as part of a β-fluoroamine motif, in a triazolium pre-catalyst, it was possible to modulate the behaviour of the corresponding N-heterocyclic carbene (NHC) with minimal steric alterations to the catalyst core. In this study, the effect of hydrogen to fluorine substitution was evaluated as part of a molecular editing study. X-ray crystallographic analyses of a number of derivatives are presented and the conformations are discussed. Upon deprotonation, the fluorinated triazolium salts generate catalytically active N-heterocyclic carbenes, which can then participate in the enantioselective Steglich rearrangement of oxazolyl carbonates to C-carboxyazlactones (e.r. up to 87.0:13.0).

scholarly journals Sydnone anions and abnormal N-heterocyclic carbenes of O-ethylsydnones. Characterizations, calculations and catalyses

2014 ◽  
Vol 50 (80) ◽  
pp. 11822-11824 ◽  
Author(s):  
Sascha Wiechmann ◽  
Tyll Freese ◽  
Martin H. H. Drafz ◽  
Eike G. Hübner ◽  
Jan C. Namyslo ◽  
...  
Keyword(s):  
Heterocyclic Carbenes ◽  
Catalytically Active ◽  
Pd Complexes

Sydnone anions and their deprotonated O-ethyl derivatives (aNHCs) form catalytically active Pd complexes.

N-Heterocyclic carbenes for metal-free polymerization catalysis: an update

2015 ◽  
Vol 65 (1) ◽  
pp. 16-27 ◽  
Author(s):  
Stefan Naumann ◽  
Andrew P Dove
Keyword(s):  
Heterocyclic Carbenes ◽  
Metal Free ◽  
Polymerization Catalysis

Poly(N-isopropylacrylamide-co-allylamine) (PNIPAM-co-ALA) nanospheres for the thermally triggered release of Bacteriophage K

2015 ◽  
Vol 96 ◽  
pp. 437-441 ◽  
Author(s):  
Hollie Hathaway ◽  
Diana R. Alves ◽  
Jessica Bean ◽  
Patricia P. Esteban ◽  
Khadija Ouadi ◽  
...  
Keyword(s):  
Triggered Release ◽  
Thermally Triggered

scholarly journals Catalyst Speciation during ansa-Zirconocene-Catalyzed Polymerization of 1-Hexene Studied by UV-vis Spectroscopy—Formation and Partial Re-Activation of Zr-Allyl Intermediates †

Polymers ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 936 ◽  
Author(s):  
Valentina N. Panchenko ◽  
Dmitrii E. Babushkin ◽  
John E. Bercaw ◽  
Hans H. Brintzinger
Keyword(s):  
Olefin Polymerization ◽  
The Other ◽  
Catalyst Precursor ◽  
Spectral Changes ◽  
Polymerization Catalysis ◽  
Pol I ◽  
Vis Spectroscopy ◽  
Catalytically Active ◽  
Kinetics Of ◽  
Catalyzed Polymerization

Catalyst speciation during polymerization of 1-hexene in benzene or toluene solutions of the catalyst precursor SBIZr(μ-Me)2AlMe2+ B(C6F5)4− (SBI = rac-dimethylsilyl-bis(1-indenyl)) at 23 °C is studied by following the accompanying UV-vis-spectral changes. These indicate that the onset of polymerization catalysis is associated with the concurrent formation of two distinct zirconocene species. One of these is proposed to consist of SBIZr-σ-polyhexenyl cations arising from SBIZr-Me+ (formed from SBIZr(μ-Me)2AlMe2+ by release of AlMe3) by repeated olefin insertions, while the other one is proposed to consist of SBIZr-η3-allyl cations of composition SBIZr-η3-(1-R-C3H4)+ (R = n-propyl), formed by σ-bond metathesis between SBIZr-Me+ and 1-hexene under release of methane. At later reaction stages, all zirconocene-σ–polymeryl cations appear to decay to yet another SBIZr-allyl species, i.e., to cations of the type SBIZr-η3-(x-R-(3-x)-pol-C3H3)+ (pol = i-polyhexenyl, x = 1 or 2). Renewed addition of excess 1-hexene is proposed to convert these sterically encumbered Zr-allyl cations back to catalytically active SBIZr-σ–polymeryl cations within a few seconds, presumably by initial 1-hexene insertion into the η1- isomer, followed by repeated additional insertions, while the initially formed, less crowded allyl cations, SBIZr-η3-(1-R-C3H4)+ appear to remain unchanged. Implications of these results with regard to the kinetics of zirconocene-catalyzed olefin polymerization are discussed.

scholarly journals Loading of Silica Nanoparticles in Block Copolymer Vesicles during Polymerization-Induced Self-Assembly: Encapsulation Efficiency and Thermally Triggered Release

2015 ◽  
Vol 137 (51) ◽  
pp. 16098-16108 ◽  
Author(s):  
Charlotte J. Mable ◽  
Rebecca R. Gibson ◽  
Sylvain Prevost ◽  
Beulah E. McKenzie ◽  
Oleksandr O. Mykhaylyk ◽  
...  
Keyword(s):  
Block Copolymer ◽  
Silica Nanoparticles ◽  
Self Assembly ◽  
Encapsulation Efficiency ◽  
Triggered Release ◽  
Thermally Triggered
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