Monitoring of the Phosphine Role in the Mechanism of Palladium-Catalyzed Benzosilole Formation from Aryloxyethynyl Silanes

Understanding the formation of benzosiloles by the intramolecular palladium-catalyzed annulation of alkynyl­(aryl)­silanes is crucial for achieving synthetic diversity toward the enhancement of the chemistry of siloles. By a combination of density functional theory calculations and experiments, we describe not only the whole mechanism of reaction but also the drawbacks that block this type of reaction. We also unravel the role of the phosphine ligand, without which the reactions could not go forward. Moreover, in silico predictive catalysis is presented here since the substitution of the phosphine ligand by an N-heterocyclic carbene (NHC) promises milder experimental conditions. A screening of substrates with different electronic properties was carried out to further understand the two fundamental steps of the reaction: stereoisomerization and concerted metalation–deprotonation.