/pdf/aryl-aryl-bond-formation-one-century-after-the-discovery-of-1jdyxlkwix.pdf

Aryl-aryl bond formation one century after the discovery of the Ullmann reaction.

Fluorine is the most electronegative element in the periodic table. When bound to carbon it forms the strongest bonds in organic chemistry and this makes fluorine substitution attractive for the development of pharmaceuticals and a wide range of speciality materials. Although highly polarised, the C–F bond gains stability from the resultant electrostatic attraction between the polarised Cδ+ and Fδ– atoms. This polarity suppresses lone pair donation from fluorine and in general fluorine is a weak coordinator. However, the C–F bond has interesting properties which can be understood either in terms of electrostatic/dipole interactions or by considering stereoelectronic interactions with neighbouring bonds or lone pairs. In this tutorial review these fundamental aspects of the C–F bond are explored to rationalise the geometry, conformation and reactivity of individual organofluorine compounds.

Understanding organofluorine chemistry. An introduction to the C–F bond

4.2.8. Reductive Coupling 3109 5. Reaction of Aromatic Compounds 3110 5.1. Electrophilic Substitutions 3110 5.2. Radical Substitution 3111 5.3. Oxidative Coupling 3111 5.4. Photochemical Reactions 3111 6. Reaction of Carbonyl Compounds 3111 6.1. Nucleophilic Additions 3111 6.1.1. Allylation 3111 6.1.2. Propargylation 3120 6.1.3. Benzylation 3121 6.1.4. Arylation/Vinylation 3121 6.1.5. Alkynylation 3121 6.1.6. Alkylation 3121 6.1.7. Reformatsky-Type Reaction 3122 6.1.8. Direct Aldol Reaction 3122 6.1.9. Mukaiyama Aldol Reaction 3124 6.1.10. Hydrogen Cyanide Addition 3125 6.2. Pinacol Coupling 3126 6.3. Wittig Reactions 3126 7. Reaction of R,â-Unsaturated Carbonyl Compounds 3127

Organic Reactions in Aqueous Media with a Focus on Carbon−Carbon Bond Formations: A Decade Update

Over the past decade, the most significant, conceptual advances in the field of fluorination were enabled most prominently by organo- and transition-metal catalysis. The most challenging transformation remains the formation of the parent C-F bond, primarily as a consequence of the high hydration energy of fluoride, strong metal-fluorine bonds, and highly polarized bonds to fluorine. Most fluorination reactions still lack generality, predictability, and cost-efficiency. Despite all current limitations, modern fluorination methods have made fluorinated molecules more readily available than ever before and have begun to have an impact on research areas that do not require large amounts of material, such as drug discovery and positron emission tomography. This Review gives a brief summary of conventional fluorination reactions, including those reactions that introduce fluorinated functional groups, and focuses on modern developments in the field.

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Introduction of Fluorine and Fluorine-Containing Functional Groups

: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

This review deals with general and significant developments in the area of building block chemistry of lightly-fluorinated aliphatic compounds, that is, those that contain one, two, or three, fluorine atoms. For the purposes of the review, building blocks are small readily-available materials that already contain fluorine atoms. They are classified according to the number of carbon atoms supplied to the target molecule, rather than according to the number of fluorine atoms. Finally, certain fluorinated motifs which may be generated easily, and are then transformable in useful ways, are discussed.

Building Block Approaches to Aliphatic Organofluorine Compounds

http://www.rsc.org/suppdata/cc/c1/c1cc11230a/c1cc11230a.pdf

What is the initiation step of the Grubbs-Hoveyda olefin metathesis catalyst?

New fluorine-containing building blocks from trifluoroethanol. 1

The potential energy surfaces for the activation of Grubbs–Hoveyda-type precatalysts with the substrates ethene, propene, 1-hexene, and ethyl vinyl ether (EVE) have been probed at the density functional theory (DFT) (M06-L) level. The energetically favored pathway of the reaction leading to a 14e Fischer carbene and styrene starts with an initiation step in which the incoming substrate and outgoing alkene ligand are both clearly associated with the ruthenium center. For these substrates, with the exception of ethene, the rate determining step is predicted to be the formation of the metallocyclobutane (MCB). We have taken the initial reactant to be a weak van der Waals complex between substrate and precatalyst. This model yields good agreement between the computed activation parameters for both the parent Grubbs–Hoveyda and Grela complex with EVE substrate, and the experimental values, reported here. The alternative model which takes the initial reactant to be two isolated molecules requires an estimate of...

Olefin Metathesis by Grubbs–Hoveyda Complexes: Computational and Experimental Studies of the Mechanism and Substrate-Dependent Kinetics

Readily prepared primary, secondary, and tertiary difluoroallylic alcohols, derived from commercially available and inexpensive 2,2,2-trifluoroethanol, have been transformed into a range of difluoroallylic methyl ethers containing appropriate carbanion-stabilizing substituents. The [2,3]-Wittig rearrangements of these difluoroallylic ethers have been achieved cleanly, using lithium diisopropylamide in tetrahydrofuran at −30 °C, in excellent (secondary ether substrates) to good (primary and tertiary ether substrates) yields. Consequently, the approach allows convenient and rapid access to products containing a mid-chain CF2 group and with a useful level of functionality.

Jonathan M. Percy

Papers

Building Block Approaches to Aliphatic Organofluorine Compounds

What is the initiation step of the Grubbs-Hoveyda olefin metathesis catalyst?

New fluorine-containing building blocks from trifluoroethanol. 1

Olefin Metathesis by Grubbs–Hoveyda Complexes: Computational and Experimental Studies of the Mechanism and Substrate-Dependent Kinetics

[2,3]-Wittig Rearrangements of Difluoroallylic Ethers. A Facile Entry to Highly Functionalized Molecules Containing a CF2 Group