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We report a transition metal-catalyzed ring expansion of azulene that can be contrasted with C–H functionalization. This study represents the first example of the successful ring expansion of azulene using Cu(hfacac)2 (hfacac: hexafluoroacetylacetonate) with a diazo reagent. This result is notable for extending the Buchner reaction, previously limited to benzenoid aromatics, to nonbenzenoid compounds. The chemoselectivity of the reaction can be directed towards C–H functionalization by substituting the Cu catalyst with AgOTf. This approach does not require the addition of phosphine, NHC, or related ligands, and prefunctionalization of azulenes is unnecessary. Furthermore, the method exhibits excellent functional group tolerance, allowing for the synthesis of a wide range of 6,7-bicyclic compounds and C–H functionalized azulenes. We also present a theoretical study that explains the experimental observations, explaining why copper afford the ring expansion product while silver forms the C–H alkylation product. Fused carbocycles are key structural elements of molecules in nature and they are often found in drugs and organic materials, but bicyclic systems containing six and seven-membered rings are difficult to prepare. Here, the authors functionalize an azulene skeleton that consists of fused five and seven-membered rings and carry out a ring expansion reaction to afford the desired bicycles. [ABSTRACT FROM AUTHOR]

A synthetic method for ethyl 4‐(alkyl or arylsulfonamido)‐2‐naphthoates from ethyl (E)‐α‐ethynyl‐β‐aryl‐α,β‐unsaturated esters (1) and N‐sulfonyl azides (2) in the presence of 2,6‐lutidine in THF at 60 °C for 3 h was developed in one step, in which a copper(I)‐catalyzed 1,3‐dipolar cycloaddition, ketenimine formation, and 6π‐electrocyclization followed by [1,3]‐H shift tandem reaction took place. This method enabled efficient synthesis of a wide range of 1‐aminonaphthalene and 3‐aminobenzofuran and 3‐aminobenzothiophene derivatives with the release of molecular nitrogen. [ABSTRACT FROM AUTHOR]