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Your search keyword '"Catherine S.J. Cazin"' showing total 3 results
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3 results on '"Catherine S.J. Cazin"'

1. [Pd(NHC)(μ-Cl)Cl]2: Versatile and Highly Reactive Complexes for Cross-Coupling Reactions that Avoid Formation of Inactive Pd(I) Off-Cycle Products

Author

Tongliang Zhou, Siyue Ma, Fady Nahra, Alan M.C. Obled, Albert Poater, Luigi Cavallo, Catherine S.J. Cazin, Steven P. Nolan, and Michal Szostak

Subjects
Chemistry, Inorganic Chemistry, Catalysis, Organic Synthesis, Science
Abstract

Summary: The development of more reactive, general, easily accessible, and readily available Pd(II)–NHC precatalysts remains a key challenge in homogeneous catalysis. In this study, we establish air-stable NHC–Pd(II) chloro-dimers, [Pd(NHC)(μ-Cl)Cl]2, as the most reactive Pd(II)–NHC catalysts developed to date. Most crucially, compared with [Pd(NHC)(allyl)Cl] complexes, replacement of the allyl throw-away ligand with chloride allows for a more facile activation step, while effectively preventing the formation of off-cycle [Pd2(μ-allyl)(μ-Cl)(NHC)2] products. The utility is demonstrated via broad compatibility with amide cross-coupling, Suzuki cross-coupling, and the direct, late-stage functionalization of pharmaceuticals. Computational studies provide key insight into the NHC–Pd(II) chloro-dimer activation pathway. A facile synthesis of NHC–Pd(II) chloro-dimers in one-pot from NHC salts is reported. Considering the tremendous utility of Pd-catalyzed cross-coupling reactions and the overwhelming success of [Pd(NHC)(allyl)Cl] precatalysts, we believe that NHC–Pd(II) chloro-dimers, [Pd(NHC)(μ-Cl)Cl]2, should be considered as go-to precatalysts of choice in cross-coupling processes.

Published
2020
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2. The effect of cocoa alkalization on the non-volatile and volatile mood-enhancing compounds

Author

Eleni Sioriki, Emmy Tuenter, Davy Van de Walle, Valérie Lemarcq, Catherine S.J. Cazin, Steven P. Nolan, Luc Pieters, and Koen Dewettinck

Subjects
Volatiles, Technology and Engineering, ALKYLPYRAZINES, IMPACT, Phytochemicals, Non-volatiles, BEANS, Gas Chromatography-Mass Spectrometry, Analytical Chemistry, Alkalization, ANTIOXIDANT CAPACITY, Cocoa, Mood, Medicine and Health Sciences, COLOR, Chocolate, Cacao, Volatile Organic Compounds, Pharmacology. Therapy, Polyphenols, General Medicine, FLAVANOL, PRODUCTS, Chemistry, Odorants, CHOCOLATE, Food Science
Abstract

Alkalization is a process to improve color, dispersibility and flavor of cocoa powder but is likely to have a negative effect on the phytochemicals. Hereto, the impact of alkalization degree (none, medium and high) on the potential mood-enhancing compounds corresponding to the four levels of the mood pyramid model (flavanols, methylxanthines, biogenic amines and orosensory properties) was investigated. The phytochemical content, analyzed via UPLC-HRMS, showed reduction of specific potential mood-enhancing compounds upon alkalization, implying a decrease in bitterness and astringency. Moreover, volatile compounds analysis via HS-SPME-GC–MS indicated that alkalization reduced the levels of volatile compounds, responsible for acidity, fruity, floral and cocoa aromas. With respect to the orosensory properties, the cocoa powder palatability was suggested to be increased due to reduced acidity, bitterness, and astringency, while the desired volatile compounds were reduced. However, sensorial analysis is required to link the volatile results with the overall effect on the flavor perception.

Published
2021

3. N-Heterocyclic Carbenes in Transition Metal Catalysis and Organocatalysis

Author

Catherine S.J. Cazin and Catherine S.J. Cazin

Subjects
Heterocyclic compounds, Carbenes (Methylene compounds), Transition metal catalysts
Abstract

N-Heterocyclic Carbenes in Transition Metal Catalysis and Organocatalysis features all catalytic reactions enabled by N-heterocyclic carbenes (NHCs), either directly as organocatalysts or as ligands for transition metal catalysts. An explosion in the use of NHCs has been reported in the literature during the past seven years making this comprehensive overview highly apropos.The book begins with an introductory overview of NHCs which could have been subtitled all you need to know about NHCs. The main body of the book is dedicated to applications of NHCs in catalysis. In addition to the success stories of NHCs in metathesis, NHCs in cross coupling and more recently NHCs in organocatalysis, all other less publicized areas are also covered. As the success of NHCs is generally attributed to their potential to stabilize metal centres, the inclusion of a chapter on the decomposition of NHC catalysts is pertinent. The book closes with a chapter describing the applications of NHCs in industrial processes, which is the first coverage of its kind, and brings a unique industrial context to this book.Included in this book:Historical aspects of NHCsSynthetic pathways to NHC precursors, free NHCs and complexesMethods of characterisation of NHCs and related complexesElectronic properties of NHCsSteric properties of NHCs and models for their descriptionNHCs for metathesis and cross-coupling reactionsNHCs as organocatalystsNHC Transition-Metal mediated oxidations, additions to multiple bonds, polymerisation and oligomerisation, cyclisations, direct arylations, reactions involving CO, C-F and C-H bond activation, …Decomposition of NHC-containing catalystsIndustrial applications involving NHC-containing catalystsN-Heterocyclic Carbenes in Transition Metal Catalysis and Organocatalysis provides a fresh view of NHCs since most contributors are young emerging researchers in the field of homogeneous catalysis using NHCs. This group of contributors is complemented by highly established academic researchers and an industrialist. This book is comprehensive, from the basic features of NHCs to the latest advances, hence it is suitable for both the novice and the expert.

Published
2011

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