Tropones make up a significant class of seven-membered non-benzenoid aromatic compounds that can be subjected to higher order cycloaddition reactions to provide a large number of biologically active compounds and natural products. Aminotroponimines derived from tropolone having a 2-hydroxy group are also a typical group of ligands. In this regard, introduction of new functional groups onto tropone and transformation of previously present functional groups in the troponoid family are desirable. Although there are several methodologies for the preparation of functionalized tropones in the literature, the development of new and convenient methods to prepare them is imperative.
For this reason, we have developed the Rh-catalyzed reaction of tropolones with N-tosyl-1,2,3-triazoles for the synthesis of the 2-functionalized aminotropones via tandem Rh-catalyzed O−H insertion, intramolecular 1,8-addition, and rearrangement in one pot. Sequential Cu-catalyzed [3 + 2] cycloaddition, Rh-catalyzed O−H insertion, intramolecular 1,8-addition, and rearrangement starting from 1-alkynes, N-sulfonyl azides, and tropolones is also demonstrated for the synthesis of the 2-functionalized aminotropones in one pot. These results suggest that sequential functionalization of O−H and C(sp2)−O bonds smoothly take place in C(sp2)−O−H bonds at the 2-position of tropolone.