A New Method for C−H Functionalization of Aliphatic Compounds by an Unusual Photochemical Reaction of Diazoketones without Elimination of Nitrogen

Benzophenone‐sensitized reactions of 4‐diazotetrahydrofuran‐3(2 H )‐ones with H‐donors such as tetrahydrofuran, 1,4‐dioxane, cyclohexane and diethyl ether, occur without elimination of nitrogen and give rise to the corresponding N‐substituted hydrazones or bis‐hydrazonoethanes due to a formal insertion of the terminal N atom of diazo group into α‐C−H bonds of ethers and aliphatic hydrocarbons, with yields of up to 78 %. Long‐wavelength UV irradiation ( λ >310 nm) is most suitable for this process, whereas oxygen molecules adequately quench the triplet excited state of the diazoketone and reduce the preparative yields of C−H‐insertion products. Hence this photochemical reaction of diazoketones can be used for C−H functionalization of different aliphatic compounds.