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Highly regio-, diastereo- and enantioselective iron-catalyzed sequential hydrosilylation of o-alk-n-enyl-phenyl silanes with alkynes is reported for various 5-, 6-, and 7-membered benzosilacycles in 60-94% yields with up to 95:5 rr, 95:5 dr, and 99% ee. Chiral fully carbon-substituted silicon-stereogenic benzosilacycles could also be obtained via triple hydrosilylation reactions. The unique electronic effect of ligands is observed while adjusting the regioselectivity and enantioselectivity in hydrosilylation reactions. A possible mechanism has been proposed by variable time normalization analysis (VTNA) and H/D exchange experiment. Benzosilacycles are of potential interest in drug discovery and materials science, and they are often synthesized through transition-metal cyclizations. Here, the authors report iron-catalyzed sequential hydrosilylations of alkynes to access various 5-, 6-, 7- and 10-membered benzosilacycles in high yield and selectivity.
Wang et al. (Fri,) studied this question.