Direct Amidation of Esters by Ball Milling**

Sustainable and solvent-free synthesis of molecules of pharmaceutical importance by ball milling

The solvent-free mechanochemical reactions under ball milling have emerged as a promising alternative to traditional solution-based chemistry. This approach not only eliminates the necessity for large quantities of solvents and minimizes waste production, but it also facilitates a unique reaction environment that enables strategies, reactions, and compound syntheses that are typically unattainable in solution. This solvent-less synthetic strategy under ball-milling has been well employed in synthetic organic chemistry in accessing various potential organic molecules including pharmaceutically important molecules and pharmaceuticals or drug-molecules. This review highlights the potential of ball milling in the synthesis of pharmaceutically important classes of molecules without using any solvent (solvent-free conditions).

Solvent‐Free Synthesis of Core‐Functionalised Naphthalene Diimides by Using a Vibratory Ball Mill: Suzuki, Sonogashira and Buchwald–Hartwig Reactions

Solvent‐free synthesis by using a vibratory ball mill (VBM) offers the chance to access new chemical reactivity, whilst reducing solvent waste and minimising reaction times. Herein, we report the core functionalisation of N,N’‐bis(2‐ethylhexyl)‐2,6‐dibromo‐1,4,5,8‐naphthalenetetracarboxylic acid (Br₂‐NDI) by using Suzuki, Sonogashira and Buchwald–Hartwig coupling reactions. The products of these reactions are important building blocks in many areas of organic electronics including organic light‐emitting diodes (OLEDs), organic field‐effect transistors (OFETs) and organic photovoltaic cells (OPVCs). The reactions proceed in as little as 1 h, use commercially available palladium sources (frequently Pd(OAc)₂) and are tolerant to air and atmospheric moisture. Furthermore, the real‐world potential of this green VBM protocol is demonstrated by the double Suzuki coupling of a monobromo(NDI) residue to a bis(thiophene) pinacol ester. The resulting dimeric NDI species has been demonstrated to behave as an electron acceptor in functioning OPVCs.

Plasma flow chemistry for direct N-acylation of amines by esters

The direct N-acylation of amines by esters in a microreactor is described using argon plasma, thereby producing amides in good to excellent yields.