Multi-faceted reactivity of -fluorobenzenesulfonimide (NFSI) under mechanochemical conditions: fluorination, fluorodemethylation, sulfonylation, and amidation reactions.

In the search for versatile reagents compatible with mechanochemical techniques, in this work we studied the reactivity of -fluorobenzenesulfonimide (NFSI) by ball milling. We corroborated that, by mechanochemistry, NFSI can engage in a variety of reactions such as fluorinations, fluorodemethylations, sulfonylations, and amidations. In comparison to the protocols reported in solution, the mechanochemical reactions were accomplished in the absence of solvents, in short reaction times, and in yields comparable to or higher than their solvent-based counterparts.

A Detailed Kinetico-Mechanistic Investigation on the Palladium C-H Bond Activation in Azobenzenes and Their Monopalladated Derivatives.

Palladium C-H bond activation in azobenzenes with R and R at positions of the phenyl rings (R = NMe, R = H (); R = NMe, R = Cl (); R = NMe, R = I (); R = NMe, R = NO (); R = H, R = H ()) and their monopalladated derivatives, using -[PdCl(DMF)], has been studied in detail by H NMR spectroscopy in -dimethylformamide- (DMF-) at room temperature; the same processes have been monitored in parallel via time-resolved UV-vis spectroscopy in DMF at different temperatures and pressures. The final goal was to achieve, from a kinetico-mechanistic perspective, a complete insight into previously reported reactivity results. The results suggest the operation of an electrophilic concerted metalation-deprotonation mechanism for both the mono- and dipalladation reactions, occurring from the coordination compound and the monopalladated intermediates, respectively.

Controlling the Polymorphism and Topology Transformation in Porphyrinic Zirconium Metal-Organic Frameworks via Mechanochemistry.

Tetratopic porphyrin-based metal-organic frameworks (MOFs) represent a particularly interesting subclass of zirconium MOFs due to the occurrence of several divergent topologies. Control over the target topology is a demanding task, and reports often show products containing phase contamination. We demonstrate how mechanochemistry can be exploited for controlling the polymorphism in 12-coordinated porphyrinic zirconium MOFs, obtaining pure hexagonal PCN-223 and cubic MOF-525 phases in 20-60 min of milling.

Protonation and Anion Binding Properties of Aromatic Bis-Urea Derivatives-Comprehending the Proton Transfer.

A series of aromatic bis-urea derivatives was prepared and their proton dissociation, as well as anion binding properties in DMSO were investigated. To this end, UV/Vis and H NMR spectroscopies and computational methods were employed. The synthesized molecules differed in the relative position of the urea moieties (ortho- and meta-derivatives) and in the functional groups (-H, -CH , -OCH , -NO ) in the para-position of the pendant phenyl groups.

Isotope Labeling Reveals Fast Atomic and Molecular Exchange in Mechanochemical Milling Reactions.

Using tandem in situ monitoring and isotope-labeled solids, we reveal that mechanochemical ball-milling overcomes inherently slow solid-state diffusion through continuous comminution and growth of milled particles. This process occurs with or without a net chemical reaction and also occurs between solids and liquid additives that can be practically used for highly efficient deuterium labeling of solids. The presented findings reveal a fundamental aspect of milling reactions and also delineate a methodology that should be considered in the study of mechanochemical reaction mechanisms.

Mechanochemical carbon-carbon bond formation that proceeds via a cocrystal intermediate.

We report the first cocrystal as an intermediate in a solid-state organic reaction wherein molecules of barbituric acid and vanillin assume a favorable orientation for the subsequent Knoevenagel condensation.

Mechanism of Mechanochemical C-H Bond Activation in an Azobenzene Substrate by Pd Catalysts.

Mechanism of C-H bond activation by various Pd catalysts under milling conditions has been studied by in situ Raman spectroscopy. Common Pd precursors, that is PdCl , [Pd(OAc) ] , PdCl (MeCN) and [Pd(MeCN) ][BF ] , have been employed for the activation of one or two C-H bonds in an unsymmetrical azobenzene substrate. The C-H activation was achieved by all used Pd precursors and their reactivity increases in the order [Pd(OAc) ] View Article and Find Full Text PDF

Neutral glycoconjugated amide-based calix[4]arenes: complexation of alkali metal cations in water.

Cation complexation in water presents a unique challenge in calixarene chemistry, mostly due to the fact that a vast majority of calixarene-based cation receptors is not soluble in water or their solubility has been achieved by introducing functionalities capable of (de)protonation. Such an approach inevitably involves the presence of counterions which compete with target cations for the calixarene binding site, and also rather often requires the use of ion-containing buffer solutions in order to control the pH. Herein we devised a new strategy towards the solution of this problem, based on introducing carbohydrate units at the lower or upper rim of calix[4]arenes which comprise efficient cation binding sites.

Dehydroacetic Acid Derivatives Bearing Amide or Urea Moieties as Effective Anion Receptors.

Derivatives of dehydroacetic acid comprising amide or urea subunits have been synthesized and their anion-binding properties investigated. Among a series of halides and oxyanions, the studied compounds selectively bind acetate and dihydrogen phosphate in acetonitrile and dimethyl sulfoxide. The corresponding complexation processes were characterized by means of H NMR titrations, which revealed a 1:1 complex stoichiometry in most cases, with the exception of dihydrogen phosphate, which formed 2:1 (anion/ligand) complexes in acetonitrile.