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

• Published in: Chemistry : a European journal 2022-09, Vol.28 (49), p.e202201444-n/a
• Main Authors: Panther, Lydia A., Guest, Daniel P., McGown, Andrew, Emerit, Hugo, Tareque, Raysa Khan, Jose, Arathy, Dadswell, Chris M., Coles, Simon J., Tizzard, Graham J., González‐Méndez, Ramón, Goodall, Charles A. I., Bagley, Mark C., Spencer, John, Greenland, Barnaby W.
• Format: Article
• Language: English
• Subjects: Atmospheric moisture; ball milling; Chemical reactions; Chemical synthesis; Chemistry; core-functionalised naphthalene diimide; Coupling; coupling reactions; Diimide; Field effect transistors; green chemistry; Moisture effects; Naphthalene; Organic light emitting diodes; Palladium; Photovoltaic cells; Photovoltaics; solid-phase synthesis; Solvents
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.202201444

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. The solvent‐free synthesis of core‐functionalised naphthalene diimide (c‐NDI) residues in a vibratory ball mill is reported. Twenty‐one naphthalene diimide‐based products were produced by using Suzuki, Sonogashira and Buchwald‐Hartwig palladium coupling reactions, including dimeric diimide products that are constituents in functioning organic photovoltaic solar cells. These reactions are rapid (60 to 90 minutes), do not require additional heating, and are tolerant of air and atmospheric moisture.