Nickel-Catalyzed 1,2-Diarylation of Alkenyl Carboxylates: A Gateway to 1,2,3-Trifunctionalized Building Blocks

A nickel-catalyzed conjunctive cross-coupling of alkenyl carboxylic acids, aryl iodides, and aryl/alkenyl boronic esters is reported. The reaction delivers the desired 1,2-diarylated and 1,2-arylalkenylated products with excellent regiocontrol. To demonstrate the synthetic utility of the method, a representative product is prepared on gram scale and then diversified to eight 1,2,3-trifunctionalized building blocks using two-electron and one-electron logic. Using this method, three routes toward bioactive molecules are improved in terms of yield and/or step count. This method represents the first example of catalytic 1,2-diarylation of an alkene directed by a native carboxylate group.     

Cu‐Catalyzed Diastereo‐ and Enantioselective Reactions of γ,γ‐Disubstituted Allyldiboron Compounds with Ketones

A catalytic diastereo‐ and enantioselective method for the preparation of complex tertiary homoallylic alcohols containing a vicinal quaternary carbon stereogenic center and a versatile alkenylboronic ester is disclosed. Transformations are promoted by 5 mol % of a readily available copper catalyst bearing a bulky monodentate phosphoramidite ligand, which is essential for attaining both high dr and er. Reactions proceed with a wide variety of ketones and allylic 1,1‐diboronate reagents, which enables the efficient preparation of diverse array of molecular scaffolds.     

On the Role of Symmetry in Vibrational Strong Coupling: The Case of Charge‐Transfer Complexation

It is well known that symmetry plays a key role in chemical reactivity. Here we explore its role in vibrational strong coupling (VSC) for a charge‐transfer (CT) complexation reaction. By studying the trimethylated‐benzene–I₂ CT complex, we find that VSC induces large changes in the equilibrium constant K_DA of the CT complex, reflecting modifications in the ΔG° value of the reaction. Furthermore, by tuning the microfluidic cavity modes to the different IR vibrations of the trimethylated benzene, ΔG° either increases or decreases depending only on the symmetry of the normal mode that is coupled. This result reveals the critical role of symmetry in VSC and, in turn, provides an explanation for why the magnitude of chemical changes induced by VSC are much greater than the Rabi splitting, that is, the energy perturbation caused by VSC. These findings further confirm that VSC is powerful and versatile tool for the molecular sciences.     

Miniemulsion polymerization of methyl methacrylate with dodecyl mercaptan as cosurfactant

Miniemulsions of methyl methacrylate with sodium lauryl sulfate as the surfactant and dodecyl mercaptan (DDM) as the cosurfactant (or hydrophobe) were prepared and polymerized. The emulsions were of a droplet size range common to miniemulsions and exhibited long-term stability (greater than 3 months). Results indicate that DDM retards Ostwald ripening and allows the production of stable miniemulsions. When these emulsions were initiated, particle formation occurred predominantly by monomer droplet nucleation. The effects of the concentration of surfactant, cosurfactant and initiator were determined. Rates of polymerization, monomer droplet sizes, polymer particle sizes, molecular weights of the polymer, and the effect of initiator concentration on the number of particles vary systematically in ways that indicate predominant droplet nucleation in these systems. © 1996 John Wiley & Sons, Inc.     

Biimidazol-2-yl–BF2 complexes

Nonfluorescent 4,4′,5,5′-tetramethyl- and 4,5,4′,5′-bistetramethylene biimidazol-2-yls 5 and 6 combined with boron trifluoride to give the tetramethyl and bistetramethylenebiimidazol-2-yl–BF₂ complexes 9 and 10 isolated as strongly fluorescent BF₃ salts, λ_f (dichloromethane): 377 nm Φ 0.93 and 386 nm Φ 0.90. Similarly, fluorescent bibenzimidazol-2-yl 7 , λ_f (ethanol), 370 nm Φ 0.14, gave a BF₂ complex 11 isolated as a BF₃ salt λ_f (ethanol), 417 nm Φ 0.68.