Blue‐Light‐Induced Carbene‐Transfer Reactions of Diazoalkanes

: Carbenes are very important reactive intermediates to access a variety of complex molecules and are applied widely in organic synthesis and drug discovery. Typically, their chemistry is accessed by the use of transition metal catalysts. Herein, we describe the application of low-energy blue light for the photochemical generation of carbenes from donor-acceptor diazoalkanes. This catalyst-free and operationally simple approach enables highly efficient cyclopropenation reactions with alkynes and the rearrangement of sulfides under mild reaction conditions, which can be utilized for both batch and continuous-flow processes.