“…In these transformations, acid or base can promote homologation of diazo compounds with ketones, which insert into C–C bonds through a carbene-free process . Notably, transition metals with diazo compounds are able to form energetic carbenoids that can formally insert into the C–C bonds, producing homologues plus one carbon . This one-carbon insertion strategy not only allows selective cleavage of inert C–C bonds but also forms functionally all-carbon quaternary centers. , However, the strained system is commonly required as it can provide a pivotal thermodynamic driving force through strain release. − In 2018, Bi and co-workers reported the first Ag-catalyzed one-carbon insertion into the unstrained C(CO)–C bonds of 1,3-dicarbonyl compounds using diazoes (the left of Figure c). , Subsequently, Cheng’s group developed an unparalleled Rh-catalyzed multicomponent assembly reaction of 1,3-diones, diazoesters, and N , N -dimethylformamide via insertion of O –C(sp 3 )–C(sp 2 ) into unstrained C(CO)–C bonds (the right of Figure c) .…”