Redox reactions of small organic molecules using ball milling and piezoelectric materials

Abstract

Over the past decade, photoredox catalysis has harnessed light energy to accelerate bond-forming reactions. We postulated that a complementary method for the redox-activation of small organic molecules in response to applied mechanical energy could be developed through the piezoelectric effect. Here, we report that agitation of piezoelectric materials via ball milling reduces aryl diazonium salts. This mechanoredox system can be applied to arylation and borylation reactions under mechanochemical conditions.

Piezocatalysis and Piezo‐Photocatalysis: Catalysts Classification and Modification Strategy, Reaction Mechanism, and Practical Application

“…© 2020 Wiley-VCH GmbH synthesis using powder catalyst. [200] It showed extreme high selectivity and reaction rate in arylation and borylation (Figure 22g). It is more practical and efficient than photocatalysis and mechano-catalysis processes.…”

Light‐ and Manganese‐Initiated Borylation of Aryl Diazonium Salts: Mechanistic Insight on the Ultrafast Time‐Scale Revealed by Time‐Resolved Spectroscopic Analysis

“…[13,18,19] These findingst herefores how that it is critical to understand how the photochemical activation is being executed, under specific conditions, as radicala nd cationic pathways might be similarly energetically feasible. Furthermore, otherr esearch teamsh ave developed non-photoinduced processes for the synthesis of aryl boronates from aryl diazonium salts, [20][21][22][23][24][25] including the one-pot diazotization/borylation of anilines, [26][27][28][29][30] proceeding via both radical and cationic intermediates.…”

Electro‐Mechanochemical Atom Transfer Radical Cyclizations using Piezoelectric BaTiO3

“…Systematic fine-tuning of the milling parameters led to the identification of the best ATRC conditions to convert monobromoacetamides 1 a-d into the corresponding lactams 2 a-d in good yields. The results of this proof-ofconcept study demonstrate the feasibility to productively merge electro-and mechanical activation modes in mechanochemical reactions by ball milling, and will certainly guide future studies on the use of piezoelectric materials not only as additives [16] but also, as in the present work, in a catalytic fashion.…”

“…[7c] Moreover, while this work was reviewed, Ito and co-workers reported the ability of cub-BaTiO 3 to reduce aryl diazonium salts upon ball milling. [16] Importantly, the ability of piezoelectric materials to effectively trigger reaction by mechanochemistry is expected to depend not only on the polarizability of the material (that is, their dielectric constants) or its crystal structure. Other parameters such as the particle size of the piezomaterial should also be considered, since mechano-induced electron transfer events between piezoelectric materials and reactants by ball milling are anticipated to occur at their interface.…”