Visible-light photocatalysis has evolved over the last decade into a widely used method in organic synthesis. Photocatalytic variants have been reported for many important transformations, such as cross-coupling reactions, α-amino functionalizations, cycloadditions, ATRA reactions, or fluorinations. To help chemists select photocatalytic methods for their synthesis, we compare in this Review classical and photocatalytic procedures for selected classes of reactions and highlight their advantages and limitations. In many cases, the photocatalytic reactions proceed under milder reaction conditions, typically at room temperature, and stoichiometric reagents are replaced by simple oxidants or reductants, such as air, oxygen, or amines. Does visible-light photocatalysis make a difference in organic synthesis? The prospect of shuttling electrons back and forth to substrates and intermediates or to selectively transfer energy through a visible-light-absorbing photocatalyst holds the promise to improve current procedures in radical chemistry and to open up new avenues by accessing reactive species hitherto unknown, especially by merging photocatalysis with organo- or metal catalysis.

Visible-Light Photocatalysis: Does It Make a Difference in Organic Synthesis?

The thermal and physicochemical properties of protic ionic liquids (PILs) are reported. It is highly evident that there has been an extensive range of alkylammonium, imidazolium, and heterocyclic cations paired with many organic and inorganic anions that have been employed to prepare PILs. There has been strong interest in modifying the properties of PILs through the addition of water or other molecular solvents. For many applications, the presence of some water in the PILs is not detrimental, and instead leads to enhanced solvent properties such as lower viscosity, higher conductivities, and lower melting points. It remains an issue of definition though of how to refer to these resulting protic solutions. There is also an ongoing difficulty surrounding how to describe the proton activity in the PILs, analogous to pH in aqueous systems. For a broad range of applications, it has been reported that the acidity/basicity of the PIL or PIL-solvent system is crucial for their beneficial properties. It is expected that the fundamental properties of PILs will continue to be explored, along with continued interest in many existing and new applications, such as in electrochemistry, organic and inorganic synthesis, and biological applications. In particular, there has been a significant interest in a broad- range of PILs for use as electrolytes and incorporation in polymer electrolytes for fuel cells, and other energy storage devices.

Protic Ionic Liquids: Evolving Structure–Property Relationships and Expanding Applications

Photokatalyse mit sichtbarem Licht: Welche Bedeutung hat sie für die organische Synthese?

Organophosphorus compounds are important in everyday applications ranging from agriculture to medicine and are used in flame retardants and other materials. Although organophosphorus chemistry is known as a mature and specialized area, researchers would like to develop new methods for synthesizing organophosphorus compounds to improve the safety and sustainability of these chemical processes.The vast majority of compounds that contain a phosphorus–carbon bond are manufactured using phosphorus trichloride (PCl3) as an intermediate. However, these reactions require chlorine, and researchers would like to avoid the use of PCl3 and develop safer chemistry that also decreases energy consumption and minimizes waste. Researchers have already proposed and discussed two primary strategies based on elemental phosphorus (P4 or Pred) or on phosphine (PH3) as alternatives to PCl3. However, phosphinates, an important class of phosphorus compounds defined as any compound with a phosphorus atom attached to two oxygens, R...

Phosphinate Chemistry in the 21st Century: A Viable Alternative to the Use of Phosphorus Trichloride in Organophosphorus Synthesis.

A Pd(II)-catalyzed C–H phosphorylation reaction has been developed using heterocycle-directed ortho-palladation. Both H-phosphonates and diaryl phosphine oxides are suitable coupling partners for this reaction.

Pd(II)-catalyzed phosphorylation of aryl C-H bonds.

Two generally applicable systems have been developed for the cross-coupling of P(O)H compounds with Csp2X and related partners. Palladium catalysis using a ligand/additive combination, typically either xantphos/ethylene glycol or 1,1′-bis(diphenylphosphino)ferrocene/1,2-dimethoxyethane, with diisopropylethylamine as the base, proved to be generally useful for the synthesis of numerous PC containing compounds. Routinely, 2 mol% of catalyst are employed (less than half the amount typically employed in most other literature reports). In most cases, excellent results are obtained with a variety of electrophiles (RX, where R=alkenyl, allyl, alkynyl, etc.). The full account of our studies is disclosed, including tandem hydrophosphinylation/coupling and coupling/coupling for doubly catalytic phosphorus-carbon bond formation. The methodology compares favorably with any existing literature report. The use of an additive appears to be a generally useful strategy to control the reactivity of phosphinylidene compounds.

Phosphorus‐Carbon Bond Formation: Palladium‐Catalyzed Cross‐Coupling of H‐Phosphinates and Other P(O)H‐Containing Compounds

Palladium-catalyzed cross-coupling of H-phosphinate esters with chloroarenes.

Mechanistic Insight into the Reduction of Tertiary Phosphine Oxides by Ti(OiPr)4/TMDS

https://www.rsc.org/suppdata/gc/b9/b920324a/b920324a.pdf

Christelle Petit

Papers

Phosphorus‐Carbon Bond Formation: Palladium‐Catalyzed Cross‐Coupling of H‐Phosphinates and Other P(O)H‐Containing Compounds

Palladium-catalyzed cross-coupling of H-phosphinate esters with chloroarenes.

Mechanistic Insight into the Reduction of Tertiary Phosphine Oxides by Ti(OiPr)4/TMDS

A straightforward synthesis of unsymmetrical secondary phosphine boranes

DBU-promoted alkylation of alkyl phosphinates and H-phosphonates