Intramolecular Photochemical C−H Insertions of α-Diazocarbonyl Compounds

Intramolecular photochemical C−H insertion reactions of α-diazocarbonyl compounds are powerful synthetic transformations leading to carbon-carbon bond formation. While there are limitations in the scope of C−H bonds amenable to C−H insertion under photochemical conditions relative to metal catalysed C−H insertions, the benefits of conducting these synthetically powerful transformations in a metal-free approach offers “green” advantages. Recent advances in technology have revolutionised the potential for use of photochemical transformations in synthesis, including the wavelength control enabled by LEDs and the benefits associated with continuous flow processing which overcome many of the traditional challenges associated with synthetic photochemistry including scale-up. The potential for telescoping the synthesis of α-diazocarbonyl compounds and downstream photochemical reactions is clear. This review summarises the development of intramolecular photochemical C−H insertions and highlights the benefits of recent technological advances.