Dialkylzincs in Radical Reactions

Abstract

This review describes recent developments in the use of dialkylzincs in radical reactions. In most of the processes reported therein, dialkylzincs act simultaneously as sources of alkyl radicals, as Lewis acids, and as chain transfer agents. A parallel is drawn with the behaviour of trialkylboranes in similar reactions.

Development of zinc alkyl/air systems as radical initiators for organic reactions

“…eqn (1)), 4 and are thus considered as the initiating species in radical organic reactions. 2 R 2 Zn + O 2 → RZnOO˙ + R˙While the nature of the radical species mediating the organic reactions mentioned above 3 has not been clearly elucidated, the postulated formation of R˙ radicals as in eqn (1) is not in line with some of the recent fundamental studies which have shown that reactions between R 2 Zn and O 2 can be conducted in a highly controllable manner without any evidence for the liberation of free alkyl radicals. 4c,5,6 For example, the controlled oxygenation of lower alkyl R 2 Zn compounds (R = Me, Et, i Pr) leads selectively to alkylzinc alkoxides 5b,6a save special cases such as t Bu 2 Zn which gives t BuZnOO t Bu species.…”

Radical zinc-atom-transfer-based carbozincation of haloalkynes with dialkylzincs

“…The last few years have witnessed a gaining interest in the use of organozinc reagents as nontoxic radical precursors or mediators [1–3]. As part of this development, the so-called radical-polar reactions in which alkylzinc reagents are used as mediators in a radical transformation that affords a new zincated species, have emerged as valuable tools in synthesis.…”

Spin‐Trapping Evidence for the Formation of Alkyl, Alkoxyl, and Alkylperoxyl Radicals in the Reactions of Dialkylzincs with Oxygen

“…[10] At 290 K (entry 5), owing to the smaller amount of oxygen with respect to Me 2 Zn in excess and the very slow oxidation of the latter, only the methyl radical adduct was detected.…”

“…Keywords: EPR spectroscopy · oxygen · radical reactions · spin traps · dialkylzinc using dialkylzinc in aerobic media. [10][11][12][13][14] However the debate still continues. Recent studies by Lewiń sky and co-workers, [15] which led to the first isolation of four-coordinate zinc alkyl peroxide complexes, [15a, b] have again addressed the question of the oxidation mechanism.…”