This study focuses on the reaction mechanisms involving triphenylphosphine (PPh3 ) derivatives, benzyne, and CO2 , giving mechanistic insights into two competing pathways: Path a, which involves direct C–P bond formation, and Path b, which progresses via a [2 + 2] cycloaddition. Comprehensive computational analysis by energy decomposition analysis (EDA) and deformation density insights was employed to elucidate the electronic and steric factors influencing the reactivity and selectivity of PPh3 derivatives. The results reveal that Path b is energetically and kinetically favored. In Path a, substantial repulsive interactions (DErep), especially for electron-withdrawing substituents, hinder C–P bond formation, making this pathway unfavorable, while Path b benefits from compensatory effects between interaction energies, with electron-releasing para-substituents, such as NHMe and OMe, increasing stabilization by enhancing DEorb contributions. Substituents in meta positions show greater distortion energies (DEdist ), which limit their stabilizing effects compared to para-substituents. The deformation density analysis of transition states (TS1(b) and TS2(b)) emphasizes the crucial role of Pauli deformation (DrPauli) and orbital deformation (DrOrb) in modulating stability. Para-substituents exhibit stronger electronic effects, reducing DEint more effectively than meta-substituents, which increase DEdist . This positional dependence underscores the importance of substituent design in optimizing reactivity.

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