Generation of aryl radicals fromin situactivated homolytic scission: driving radical reactions by ball milling

Abstract

The need for an operationally straightforward application of radical chemistry has led researchers to explore practical strategies to obtain and trap radicals.

Mechanochemical Radical Boronation of Aryl Diazonium Salts Promoted by Sodium Chloride

“…However, no indication of such interaction was observed by 11 B NMR in the case of chloride ions (see Supporting Information for more details). Another support for the radical course of this process was obtained by Yu and coworkers, [33] who performed a radical trapping experiment with TEMPO in NaCl‐promoted mechanochemical transformation of diazonium salts.…”

“…During our studies, a paper on the capability of NaCl to induce aryl radical formation from diazonium salts was published by Yu and coworkers. [33] The focus of this study was mainly CÀ C bond formation, but isolated examples of CÀ S and CÀ B bonds were also reported.…”

Green metrics in Mechanochemistry

“…Yu et al 147 also reported that 1,3,5-trimethoxybenzene or indole derivatives could undergo a C-H cascade addition starting from aryldiazoniums, and styrene derivatives in the presence of NaCl (Scheme 32, Eqn 5). Direct Hydrogen Atom Transfer (HAT) addition of aryl radical was also efficient on position 3 of indoles starting from 4-hydroxystyrene derivatives (Scheme 32, Eqn 6).…”

“…Yu et al described the mechanochemical aryl radical formation by homolytic cleavage of aryldiazoniums. 147 The C-H (hetero)arylation of 1H-and 2H-indazoles, N-methyl-3methylindole, benzothiazole, 2-methylthiophene, phenyl derivatives was developped. Typically, the reaction was performed on 0.3 mmol scale (Scheme 32, Eqn 1): 4methoxyphenyldiazonium tetrafluoroborate 151 (2.5 equiv.…”

α-C–H functionalization of glycine derivatives under mechanochemical accelerated aging en route the synthesis of 1,4-dihydropyridines and α-substituted glycine esters

“…Despite the enormous advances that have been made, the use of bulk toxic solvents, metal/(photo) catalysts, external oxidative additives, and/or heating greatly depreciates the sustainability and practicality of these strategies, which calls for continuous improvement. Based on the practical requirements of green and effective synthesis of the privileged frameworks of 1,4-DHPs as well as the α-functionalized glycines, and our research interests in mechanochemistry, 17 herein, we demonstrate a novel AA facilitated (cascade) CDC of glycinates and various nucleophiles under metal-free and solvent-minimal conditions. (Fig.…”