Catalyst‐free Hantzsch Ester‐mediated Organic Transformations Driven by Visible light

Abstract In the early days of synthetic organic chemistry Hantzsch esters (HEs) were bio‐inspired hydride donors and often used for the reduction of C=X (X=C, N, O) bonds. Recently, it has been proved that HEs and their derivatives (4‐Alkyl‐ or acyl‐Hantzsch esters) serve as electron donor, proton source, hydrogen atom donor, alkyl and acyl radical precursors in photoredox catalysis. Recently it was found that the excited‐state of HEs has also been identified as a strong photo reductant in the absence of photocatalyst and also, the donor of HE forms EDA‐complexes with organic molecules and triggers SET process to generate carbon radical entities. This minireview focuses on the recent chemistry developments where Hantzsch esters act as a photo reductant in organic synthesis, with a special focus on the reaction mechanisms. We hope that this review will help in the further development of radical‐based organic transformations in absence of external photocatalysts.