Systematic studies on mechanochemical synthesis: Schiff bases from solid aromatic primary amines and aldehydes

Spontaneous Synthesis of [FeII (Atrz)3 ]SO4 and its Analogues Through Accelerated Ageing: New Insights from Small-Scale Reactions

Accelerated ageing reactions that take place between two solid materials on contact in the absence of added solvent have been used to synthesize two spin-crossover-active 1D coordination polymers and one of their Cu(II) analogues. The hygroscopy of the ligands and the relative humidity of the reaction chamber have been shown to be particularly important factors in the rate of reaction. Small-scale reactions between a few individual crystals have allowed observation of deliquescence of the 4-aminotriazole ligand at high humidity. The metal salt does not dissolve, and the ligand diffuses into the crystal of the metal salt during the reaction. In the case of the Cu analogue, the formation of the product causes the crystal of the metal salt to deform with the formation of pseudocrystals, which have a fibrous structure.

Electronic Impacts on the Solvent-Free Mechanochemical Synthesis of Salophen Ligands in Ball Mill

To realize the scope of the solid-solid reaction, the functional solid diamines reacted with solid 3-ethoxysalicylaldehyde under high-speed ball milling in a solvent-free environment. The findings showed that a wide range of Salophen ligands could be produced in good to excellent yields. In comparison to the similar Salophen synthesis to date, the current study provided solvent-free, fast reaction, high yield, and easy work-up.

Catalytic Room-Temperature C-N Coupling of Amides and Isocyanates by Using Mechanochemistry

A mechanochemical route is developed for room-temperature and solvent-free derivatization of different types of amides into carbamoyl isatins (up to 96 % conversion or yield), benzamides (up to 81 % yield), and imides (up to 92 % yield). In solution, this copper-catalyzed coupling either does not take place or requires high temperatures at which it may also be competing with alternative thermal reactivity, highlighting the beneficial role of mechanochemistry for this reaction. Such behavior resembles the previously investigated coupling with sulfonamide substrates, suggesting that this type of C-N coupling is an example of a mechanochemically favored reaction, for which mechanochemistry appears to be a favored environment over solution.