Unlocking novel reaction pathways of diazoalkanes with visible light

Photochemistry has recently attracted the interest of synthetic chemists to conduct photolysis reactions of diazoalkanes. In this feature article, we provide a concise overview on this field, starting with discoveries in physical organic chemistry and then discuss examples in organic synthesis of singlet carbene intermediates, ranging from classic reactivity towards advances in cascade reactions and unusual protonation reactions under photochemical conditions. We then commence with a discussion on the electronic control of singlet and triplet carbene intermediates and last discuss the advances that have been made with regards to the reaction of weakly colored diazoalkanes in dye-sensitized reactions to access radical or triplet carbene intermediates.