Cobalt-catalyzed intermolecular hydroacylation of aldehydes: Initiation of hydride transfer enables turnover

Intermolecular hydroacylation of aldehydes catalyzed by an in situ generated low-valent cobalt system was developed. Mechanistic studies disclosed that the desired hydroacylation was impeded by poor hydride donation by the respective Co(iii)-H phosphine complex formed by the oxidative addition of Co(i) to the formyl C-H bond. Surprisingly, the reaction rate was significantly promoted in the presence of Lewis base N,N-diisopropylethylamine (iPr₂NEt) functioning as an initiator of hydride transfer, thereby offering an excellent reaction efficiency with high substrate tolerance.