Palladium‐Catalyzed Ring Expansion of Benzosilacyclobutenes: Ligand Substituent Effects on Stereodivergent Catalysis
Wen-Jing Shang, Q.-L. Zhou, Jia‐Wei Si, Junhui Zhu, Jiyuan Lv, Li Li, Fuk Yee Kwong, Zheng Xu, Li‐Wen Xu
Abstract
Abstract Transition‐metal‐catalyzed silicon‐carbon bond activation of small silacycles has proven particularly useful in direct synthesis of silicon‐containing heterocycles. Despite significant advances in the synthesis of new silacycles based on Si─C bond activation of silacyclobutanes, a fascinating challenge lies in the construction of silicon‐stereogenic benzosilacycles from the ring expansion of racemic benzosilacyclobutenes. In this work, we present an example of palladium‐catalyzed asymmetric Si─C bond activation of racemic benzosilacyclobutenes and its ring expansion with conjugated alkynes to address this challenging enantioselective transformation, in which various benzosilacycles bearing ester groups are synthesized with promising enantioselectivity in this reaction featured with catalytic chemo‐ and stereo‐selective transformation of racemic benzosilacyclobutenes. Moreover, the outcome of stereodivergent catalysis with reversed enantioselectivity might be arose from the steric effect of large cavity on TADDOL‐derived phosphoramidite ligand.