Photocatalyzed Benzylic Fluorination: Shedding “Light” on the Involvement of Electron Transfer

The photocatalyzed oxidation of benzylic compounds by 1,2,4,5-tetracyanobenzene (TCB) in the presence of Selectfluor provides a synthetically efficient route to electron deficient, less substituted, and otherwise inaccessible benzylic fluorides. The virtue of this system is multifold: it is metal-free and mild, and the reagents are inexpensive. Mechanistically, the data suggest the intimate formation of intermediate radical cations in the key radical forming step, as opposed to a concerted hydrogen atom transfer process

A Chelating Nucleophile Plays a Starring Role: 1,8-Naphthyridine-Catalyzed Polycomponent α,α-Difluorination of Acid Chlorides

A dually activated ketene enolate, generated from an acid chloride, the unusual chelating nucleophile (1,8-naphthyridine), and a Lewis acid, reacts to afford a host of α,α-difluorinated products in the presence of a benchtop-stable fluorinating agent (Selectfluor). The use of this method to synthesize otherwise difficult to make products is highlighted along with computational and spectroscopic support for the proposed chelate

Metal-Catalyzed Benzylic Fluorination as a Synthetic Equivalent to 1,4-Conjugate Addition of Fluoride

We explore in detail the iron-catalyzed benzylic fluorination of substrates containing aromatic rings and electron-withdrawing groups positioned β to one another, thus providing direct access to β-fluorinated adducts. This operationally convenient process can be thought of not only as a contribution to the timely problem of benzylic fluorination but also as a functional equivalent to a conjugate addition of fluoride, furnishing products in moderate to good yields and in excellent selectivity

Iron(II)-Catalyzed Benzylic Fluorination

Direct C–F functionalization of benzylic sp³ C–H bonds is a synthetic challenge that has yet to be propitiously overcome. A mild, one-pot synthesis of monofluorinated benzylic substrates is reported with commercially available iron(II) acetylacetonate and Selectfluor in good to excellent yields and selectivity. A convenient route to β-fluorinated products of 3-aryl ketones is also highlighted, providing a synthetic equivalent to the difficult to accomplish conjugate addition of fluoride to α,β-unsaturated ketones

Interaction of a C–F Bond with the π-System of a CC Bond or “Head On” with a Proximate C–H Bond

We describe the synthesis and preliminary study of two molecules, in which a fluorine atom is positioned proximately above the π-orbitals of a CC bond or else wherein a C–F bond interacts in a “head on” fashion with a proximate C–H bond. The spectroscopic characteristics of these unusual interactions are documented, X-ray crystallographic analyses are reported, and theoretical calculations are employed to support the observed spectroscopy

Interaction of a C–F Bond with the π-System of a CC Bond or “Head On” with a Proximate C–H Bond

We describe the synthesis and preliminary study of two molecules, in which a fluorine atom is positioned proximately above the π-orbitals of a CC bond or else wherein a C–F bond interacts in a “head on” fashion with a proximate C–H bond. The spectroscopic characteristics of these unusual interactions are documented, X-ray crystallographic analyses are reported, and theoretical calculations are employed to support the observed spectroscopy

Interaction of a C–F Bond with the π-System of a CC Bond or “Head On” with a Proximate C–H Bond

We describe the synthesis and preliminary study of two molecules, in which a fluorine atom is positioned proximately above the π-orbitals of a CC bond or else wherein a C–F bond interacts in a “head on” fashion with a proximate C–H bond. The spectroscopic characteristics of these unusual interactions are documented, X-ray crystallographic analyses are reported, and theoretical calculations are employed to support the observed spectroscopy

Direct, Catalytic Monofluorination of sp³ C–H Bonds: A Radical-Based Mechanism with Ionic Selectivity

Recently, our group unveiled a system in which an unusual interplay between copper­(I) and Selectfluor effects mild, catalytic sp³ C–H fluorination. Herein, we report a detailed reaction mechanism based on exhaustive EPR, ¹⁹F NMR, UV–vis, electrochemical, kinetic, synthetic, and computational studies that, to our surprise, was revealed to be a radical chain mechanism in which copper acts as an initiator. Furthermore, we offer an explanation for the notable but curious preference for monofluorination by ascribing an ionic character to the transition state

Direct, Catalytic Monofluorination of sp³ C–H Bonds: A Radical-Based Mechanism with Ionic Selectivity

Recently, our group unveiled a system in which an unusual interplay between copper­(I) and Selectfluor effects mild, catalytic sp³ C–H fluorination. Herein, we report a detailed reaction mechanism based on exhaustive EPR, ¹⁹F NMR, UV–vis, electrochemical, kinetic, synthetic, and computational studies that, to our surprise, was revealed to be a radical chain mechanism in which copper acts as an initiator. Furthermore, we offer an explanation for the notable but curious preference for monofluorination by ascribing an ionic character to the transition state