α-Fluorocarbanions are key intermediates in nucleophilic fluoroalkylation reactions. Although frequently discussed, the origin of the fluorine effect on the reactivity of α-fluorinated CH acids has remained largely unexplored. We have now investigated the kinetics of a series of reactions of α-substituted carbanions with reference ... READ MORE

The kinetics and mechanism of the reactions of formyl-stabilized ylide Ph₃P=CHCHO (1) and acetyl-stabilized ylide Ph₃P=CHCOMe (2) with benzhydrylium ions (Ar₂CH⁺, 3) were investigated by UV-Vis and NMR spectroscopy.  As ambident nucleophiles, ... READ MORE

Rate and equilibrium constants for the reactions of indol-3-ylmethylium ions with triarylphosphines and pyridines were measured spectrophotometrically. The resulting Lewis acid-base adducts were characterized by NMR and X-ray crystallography. All rate constants, except those for the reactions of sterically hindered ... READ MORE

The ability to modulate the nucleophilicity and Lewis basicity of N-heterocyclic carbenes is pivotal to their application as organocatalysts. Herein we examine the impact of the N-substituent on the nucleophilicity and Lewis basicity. Four N-substituents popular in NHC organocatalysis, namely, the ... READ MORE

Kinetics and mechanisms of the reactions of the β-dicarbonyl-substituted iodonium ylides 1(a–d) with several π-conjugated carbenium and iminium ions have been investigated. All reactions proceed with rate-determining attack of the electrophile at the nucleophilic carbon center of the ylides to give iodonium ions, ... READ MORE

Kinetics of activation of methyl and benzyl metallocene precatalysts by benzhydrylium ions, tritylium ions, and triarylborane B(C₆F₅)₃ were measured spectrophotometrically. The rate constants correlate linearly with the electrophilicity parameter E of the benzhydrylium and tritylium ions ... READ MORE

Rate and equilibrium constants of the reactions of nicotine and structurally related compounds with benzhydrylium ions have been determined UV-Vis spectroscopically using stopped-flow and laser-flash techniques. The pyridine nitrogen of nicotine was identified as the site of thermodynamically and kinetically controlled attack. Quantum ... READ MORE

The kinetics of the reactions of ethenesulfonyl fluoride (ESF) with sulfonium and pyridinium ylides were measured photometrically to determine the electrophilicity parameter of ESF according to the correlation lg k_20 °C=s_N(N+E). With E=−12.09, ESF is among the ... READ MORE

The mechanistic model of Organic Chemistry is based on relationships between rate and equilibrium constants. Thus, strong bases are generally considered to be good nucleophiles and poor nucleofuges. Exceptions to this rule have long been known, and the ability of iodide ions to catalyze nucleophilic substitutions, because they are good ... READ MORE

Mesoporous silica nanoparticles (MSNs) attract increasing interest in the field of gene and drug delivery due to their versatile features as a multifunctional drug delivery platform. Here, we describe poly(amidoamine) (PAMAM) dendron-functionalized MSNs that fulfill key prerequisites for a controllable intracellular drug release. In ... READ MORE

Kinetics of the reactions of 2-substituted malonate anions and 5-substituted Meldrum's acid anions with benzhydrylium ions and structurally related quinone methides have been monitored in dimethyl sulfoxide solution at 20 °C. The resulting second-order rate constants followed the correlation lg k(20 °C) = ... READ MORE

Effective and controlled drug delivery systems with on-demand release and targeting abilities have received enormous attention for biomedical applications. Here, we describe a novel enzyme-based cap system for mesoporous silica nanoparticles (MSNs) that is directly combined with a targeting ligand via bio-orthogonal click ... READ MORE