Metal-free visible-light carbonylation of alkyl iodides to amides via consecutive photoinduced electron transfer

Abstract

A visible-light-driven, metal-free carbonylation of unactivated alkyl iodides is reported, enabling the direct synthesis of 35 structurally diverse amides in good to excellent yields. The reaction shows broad functional-group tolerance toward both amines and alkyl iodides, including bioisosteric motifs and complex natural product derivatives, underscoring its potential for late-stage functionalization. Mechanistic investigations combining flash photolysis, spectroelectrochemistry, irradiated thin-layer cyclic voltammetry, and EPR spectroscopy reveal a consecutive photoinduced electron transfer (ConPET) mechanism that diverges from conventional single-photon photoredox catalysis. DFT calculations elucidate the key radical carbonylation steps governing reactivity and selectivity. This sustainable and operationally simple method offers a transition-metal-free approach to carbonylation, expanding the toolbox for highly reducing transformations under mild conditions.