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.

The functionalization of C À Hb onds with nonprecious metal catalysts is an important researcha rea for the development of efficient and sustainable processes.Herein, we describe the development of iron porphyrin catalyzedreactions of diazoacetonitrile with N-heterocycles yielding important precursors of tryptamines,a long with experimental mechanistic studies and proof-of-concept studies of an enzymatic process with YfeX enzyme.B yu sing readily available FeTPPCl, we achieved the highly efficient CÀHfunctionalization of indole and indazole heterocycles.T hese transformations feature mild reaction conditions,e xcellent yields with broad functional group tolerance,c an be conducted on gram scale,a nd thus provide au nique streamlined access to tryptamines.

Slow addition of sodium nitrite allows the in situ preparation of highly explosive diazo compounds and enables their safe and scalable application in iron catalyzed rearrangement reactions of allylic and propargylic sulfides. With catalyst loadings as low as 0.1 mol% an effective entry into α-mercapto-nitriles, α-mercapto-esters and α-trifluoromethyl-sulfides on a gram-scale is achieved.

We report a new convenient and efficient method utilizing the tropylium ion as a mild and environmentally friendly organocatalyst to mediate retro-Claisen-type reactions.