Journal ArticleDOI
Factors Controlling the Addition of Carbon‐Centered Radicals to Alkenes—An Experimental and Theoretical Perspective
Hanns Fischer,Leo Radom +1 more
TLDR
The analysis leads to a partial revision of the previous qualitative rules, and it more clearly exhibits the interplay of the reaction enthalpy effects, polar charge-transfer contributions, and steric substituent effects on the reaction energy barrier.Abstract:
The successful exploitation of syntheses involving the generation of new carbon-carbon bonds by radical reactions rests on some prior knowledge of the rate constants for the addition of carbon-centered radicals to alkenes and other unsaturated molecules, and of the factors controlling them. Two former classical reviews in Angewandte Chemie by Tedder (1982) and by Giese (1983) provided mechanistic insight and led to various qualitative rules on the complex interplay of enthalpic, polar, and steric effects. In the meantime, the field has experienced very rapid progress: many more experimental absolute rate constants have become available, and there have been major advances in the efficiency and reliability of quantum-chemical methods for the accurate calculation of transition structures, reaction barriers, and reaction enthalpies. Herein we review this progress, recommend suitable experimental and theoretical procedures, and display representative data series for radical additions to alkenes. On this basis, and guided by the pictorial tool of the state-correlation diagram for radical additions, we then offer a new and more stringent quantification of the controlling factors. Our analysis leads to a partial revision of the previous qualitative rules, and it more clearly exhibits the interplay of the reaction enthalpy effects, polar charge-transfer contributions, and steric substituent effects on the reaction energy barrier. The various contributions are cast into the form of new, simple, and physically meaningful but non-linear, predictive equations for the preestimation of rate constants. These equations prove successful in several tests but call for additional theoretical and experimental foundation. The kinetics of related reactions such as polymer propagation, copolymerization, and the addition of radicals to alkynes and aromatic compounds is shown to follow the same principles.read more
Citations
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Journal ArticleDOI
Living radical polymerization by the RAFT process
TL;DR: A review of living radical polymerization achieved with thiocarbonylthio compounds by a mechanism of reversible addition-fragmentation chain transfer (RAFT) is presented in this article.
Journal ArticleDOI
Photoredox Catalysis in Organic Chemistry
TL;DR: This Perspective highlights the unique ability of photoredox catalysis to expedite the development of completely new reaction mechanisms, with particular emphasis placed on multicatalytic strategies that enable the construction of challenging carbon-carbon and carbon-heteroatom bonds.
Journal ArticleDOI
Living Radical Polymerization by the RAFT Process - A Second Update
TL;DR: The authors provides a third update to the review of reversible deactivation radical polymerization (RDRP) achieved with thiocarbonylthio compounds (ZC(S)SR) by a mechanism of reversible addition-fragmentation chain transfer (RAFT) that was published in June 2005.
Journal ArticleDOI
Platinum Group Organometallics Based on “Pincer” Complexes: Sensors, Switches, and Catalysts
Martin Albrecht,Gerard van Koten +1 more
TL;DR: This review discusses the synthetic methodologies that are currently available for the preparation of platinum group metal complexes containing pincer ligands and especially emphasizes different applications that have been realized in materials science such as the development and engineering of sensors, switches, and catalysts.
Journal ArticleDOI
Photochemical Reactions as Key Steps in Organic Synthesis
TL;DR: Photochemical Electron-Transfer Reactions with a Catalytic Sensitizer 1068 6.1.1 Photochemical Extrusion of Small Molecules 1067 6.2.2 Photochemical Rearrangings 1061 4.4.3.
References
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