Accelerated ageing reactions: towards simpler, solvent-free, low energy chemistry

Abstract

We provide an overview of chemical transformations that proceed spontaneously, by mixing of initially solid reactants, and are accelerated and/or directed through gentle stimuli in the form of mild heating,...

Elucidation of the Diels–Alder Reaction Kinetics between Diphenylfulvene and Maleimide by Mechanochemistry and in Solution

“…Indeed, some chemical reactions can occur spontaneously between solid reagents, in some cases facilitated by humidity, organic vapors, the addition of catalysts, heating, or brief grinding. 36 In our case, this phenomenon does not take place when diphenylfulvene and maleimide are simply mixed without previous cogrinding. So, the aging reaction was studied after 15 min and 1 h of grinding at 24 °C (Figure 8).…”

Formation of pharmaceutical salts and cocrystals via vapour-assisted tumbling (VAT) – a solvent efficient process

“…Such a phenomenon is already well-known in the pharmaceutical field as evidenced by the requirement to test and control against the interconversion of solid forms, such as hydration of an anhydrous form, that can occur upon exposure to atmospheric humidity. [10][11][12][13][14][15][16] If one could harness this vapour-assisted solid-solid conversion with other solvents, then the use of solvents could be considerably lowered. Further to this, if the material can be crystallised and dried within the same process, time and energy input are also majorly reduced.…”

A Case Study on the Desired Selectivity in Solid‐State Mechano‐ and Slow‐Chemistry, Melt, and Solution Methodologies

“…Therefore, the search for new mild and green synthetic methods continues to be a hot topic [1–3] . In this regard, solvent‐free solid‐state processes like mechanochemical synthesis [4–6] (driven by the absorption of mechanical energy) or slow‐chemistry reactions [7–9] (i. e., solid‐state transformations between two distinct solid substrates with kinetics limited by diffusion, which occur at ambient temperature without external stimuli) are one of the key targets of the green chemistry developments. In the last two decades, mechanochemistry has transformed from a mere curiosity into the complementary toolbox in synthetic organic, organometallic, and inorganic chemistry [6,10–13] as well as materials science [14,15] .…”

“…In turn, melt‐phase‐driven transformations, a subgroup of solventless reactions, have been vital in polymorph screening [19] or organic [20,21] and organometallic [22] synthesis. Furthermore, while mechanochemistry requires engagement of the mechanical stress, the core concept of slow chemistry avoids external stimuli but does not exclude acceleration of a reaction rate by the presence of a solvent vapor [8,23] . Many examples of reactions considered as slow chemistry are observed in Nature, [7] and only recently pioneering synthetic procedures mimicking natural processes in the laboratory have been reported [24–27] …”