Iridium-Catalyzed Synthesis of Diaryl Ethers by Means of Chemoselective CF Bond Activation and the Formation of BF Bonds

DFT Study on C-F Bond Activation by Group 14 Dialkylamino Metalylenes: A Competition between Oxidative Additions versus Substitution Reactions

The C-F bond activation of pentafluoropyridine (PFP) by group 14 dialkylamino metalylenes has been studied employing DFT calculations. Emphasis is placed on the group 14 central atom (M = Si^II, Ge^II, and Sn^II) and substituents (-NMe₂, -NⁱPr₂, -Cl, -NH₂, and -PH₂) dependent switching of oxidative addition to the metathesis/substitution reaction route, using state-of-the-art theoretical methods (M062X/def2-QZVP(SMD)//M062X/def2-TZVP) to provide a systematic classification of the individual mode of reactions. Moreover, an energy decomposition analysis (EDA) is implemented to get a brief insight into the physical factors that control the activation barriers originating via the different mode of reactions, viz., oxidative addition and metathesis routes. The key finding is that the distortion of PFP is the principal guiding factor in the oxidative addition reaction, while distortions imposed on both the PFP and metalylenes are inevitable toward the origin of the metathesis reaction barrier. The preferable oxidative addition reaction over metathesis of substituted silylenes can be explained on the basis of electron concentration and the HOMO-LUMO gap between the reacting substrates. However, the dramatic switch between oxidative addition and metathesis reaction in substituted germylenes depends on both the electronic and steric nature of the substituents. Similar observations are also noted for the reactivity of substituted stannylenes.

Palladium-Catalysed and Phosphine-Promoted Synthesis of Diaryl Ethers through Self-Coupling

An efficient, palladium acetate-catalysed, tributylphosphine-promoted direct synthesis of symmetrical diaryl ethers through the self-coupling of aryl fluorides has been developed with K2CO3/ZrO2 as a base. This provides an alternative method to prepare aromatic polymers, important synthetic intermediates and natural products for use in the field of pharmaceuticals and industrial materials.

Diboron(4) Compounds: From Structural Curiosity to Synthetic Workhorse

Although known for over 90 years, only in the past two decades has the chemistry of diboron(4) compounds been extensively explored. Many interesting structural features and reaction patterns have emerged, and more importantly, these compounds now feature prominently in both metal-catalyzed and metal-free methodologies for the formation of B-C bonds and other processes.