From Delocalization to Disruption: The Role of Aromaticity in -Heterocyclic Carbenes' Reactions with Diazoalkane and Diazoester.

Aromaticity is a fundamental force shaping molecular stability and reactivity, yet its dynamic role along reaction coordinates remains poorly understood. In this study, we unveil how dynamic changes in aromatic character govern the reactivity of 5-ItBu with diazoalkanes and diazoesters through a multifaceted computational approach. By integrating electronic, magnetic, structural, and energetic aromaticity descriptors, we demonstrate that the retention of aromaticity along the reaction path markedly lowers activation barriers, while its disruption imposes significant energetic penalties. Activation strain model (ASM) and energy decomposition analysis (EDA) further underscore the role of aromatic stabilization in enhancing orbital interactions that drive reactivity. These insights establish a cohesive mechanistic framework, highlighting aromaticity not merely as a static structural feature but as a tunable lever in the design of selective transformations and next-generation catalysts.