Oxidation of Alkyl Trifluoroborates: An Opportunity for Tin‐Free Radical Chemistry

Abstract

Organotrifluoroborates have been oxidized by copper(II) salts and Dess–Martin periodinane via radical intermediates, as evidenced by TEMPO spin‐trapping experiments. This new method of radical generation is compatible with functionalization and CC bond formation through Giese‐type addition reactions (see scheme; DMSO=dimethyl sulfoxide, TEMPO=2,2,6,6‐tetramethyl‐1‐piperidinyloxyl, free radical).

Direct Alkylation of Heteroaryls Using Potassium Alkyl- and Alkoxymethyltrifluoroborates

“…In accord with precedents established in previous studies,7b,8b,12,14 a possible mechanism can be proposed (Scheme 2). The first step involves a homolytic cleavage of the C-B bond using one equivalent of manganese(III) acetate.…”

Practical Radical Cyclizations with Arylboronic Acids and Trifluoroborates

“…In the case of aryl-centered radicals, diazonium salts serve as one means for entry into radical processes, although their preparation and handling offsets their synthetic value. Among the recent developments 2 aimed at circumventing such drawbacks, the recently discovered Minisci-type reactivity of organoboronic acids 3 and trifluoroborates 3b,4 (Figure 1) addresses many of these. Indeed, the conditions involve the use of ubiquitous boronic acids, cheap inorganic salts (silver nitrate and potassium persulfate), can be performed in an open-flask without recourse to high temperatures, and can be safely conducted on gram-scale.…”

Improving Transformations Through Organotrifluoroborates

“…For example, the Cu(II)-promoted oxidation of alkyltrifluoroborates to carbon radicals has been demonstrated (Scheme 42) [76]. Primary and secondary alkyltrifluoroborates served as radical precursors in the presence of either CuCl 2 , Cu(EH) 2 , or DMP (EH ¼ 2-ethyl hexanoate).…”