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. Robust and metal‐free: The photolysis of donor–acceptor diazoalkanes with low‐energy blue light provides operationally simple access to carbene‐transfer reactions. Even in the presence of moisture and air, cyclopropenation and rearrangement reactions of sulfur ylides can be performed with high efficiency in either batch or flow reactors.