1, 4‐Diaza‐1, 3‐dienes (DADs) are among the most widely used redox‐active ligands. In this study, we examine how this redox non‐innocence governs the reactivity of a DAD ligand in its enediamide dianion form, DAD 2−, toward organic carbonyl compounds. The key question is whether the enediamide dianion acts solely as an electron donor ‐ thus remaining a spectator ligand ‐ or whether it assumes an active, bond‐forming role. All reactions described herein employ the dilithium complex (THF) 2 Li 2 (t Bu‐DAD), derived from N, N′‐bis (tert‐butyl) −1, 4‐diaza‐1, 3‐diene, as an enediamide equivalent. The reaction with aldehydes or ketones (1: 1 stoichiometry) proceeds via single‐electron transfer from the enediamide moiety, coupled with CC bond formation at the carbonyl carbon, to afford trifunctional oxido amido imine products. In contrast, reaction with an ester such as ethyl acetate involves two single‐electron transfer steps, resulting in an overall two‐electron redox process and attachment of two enediamide units to the ester carbonyl carbon through newly formed CC bonds. This dual role becomes more apparent in reactions with benzyl benzoate. The product reveals that both carbon atoms of the enediamide CC unit bond to the ester carbonyl carbon accompanied by cleavage of the CC bond and formal insertion of the carbonyl carbon into the ligand backbone.
Liang et al. (Wed,) studied this question.
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