Computational Studies on the Tropylium‐Catalyzed Carboxylic Acid O−H Insertion with Diazoesters: The Role of Homoaromaticity**

Abstract A tropylium‐catalyzed carboxylic acid O−H insertion with diazoesters was reported to provide α‐hydroxy esters through an activated carbene intermediate. This study presents a revised mechanism based on density functional theory (DFT) calculations involving a unique homoaromatic intermediate formed between the tropylium ion and the diazoester. The calculated energies of the intermediates and transition states support this revised mechanism. Our computational model explains the tropylium ion‘s binding to the diazoester, resulting in the homoaromatic intermediate. By comparing the reaction profiles of four different pathways, our findings contribute to a better understanding of the reaction mechanism and have potential implications for designing more efficient catalytic systems.