DFT Study on the Role of Lewis Acids in Benzoxasilole Synthesis Via Intramolecular Hosomi–Sakurai Reaction

The reaction mechanism of the Lewis acid–catalyzed intramolecular Hosomi–Sakurai reaction of o –allylsilyl benzaldehyde has been analyzed computationally. Our calculations indicate that the reaction follows a stepwise mechanism, in which the initial formation of a bicyclic nonclassical cation after the first C─C bond formation is followed by a conformational rearrangement of the bicyclic intermediate generated and a concomitant Si─C cleavage and Si─O bond formation, ultimately yielding the final benzoxasilole. The analysis of the relationship between the energetic profile and Lewis acid structure shows that the first C─C bond formation process and the stability/reactivity of these bicyclic nonclassical cationic intermediates determine its catalytic activity.