Stereoselective Synthesis of Silylated Vinylboronates by a Boron-Wittig Reaction and Their Application to Tetrasubstituted Olefins

The highly stereoselective synthesis of a series of tetrasubstituted mono- as well as disilylated vinylboronates is reported by using the boron-Wittig approach. The condensation between acylsilanes and gem-diborylalkanes gave the desired tetrasubstituted olefins in good to excellent yield and high stereoselectivity. Also, a series of trisubstituted silylated vinyl MIDA-boronates was synthesized by using the boron-Wittig reaction followed by a transesterification reaction. This methodology allows direct incorporation of B(pin) and TMS groups in the anti-position of the olefin in a highly stereoselective manner. Further, sequential Suzuki coupling reaction with the silylated vinyl boronic esters generated all-carbon tetrasubstituted alkenes, which have been applied in the total synthesis of the anticancer drug Tamoxifen and aggregation-induced luminogen agent TPE-TF17. A series of tetrasubstituted silylated pinacol vinylboronates and trisubstituted silylated vinyl MIDA-boronates was synthesized by using the boron-Wittig approach. By using this protocol, the boryl and the silyl groups can be directly and highly stereoselectively incorporated into the olefin's anti-position. Further, sequential Suzuki coupling of the silylated vinyl boronates allows access to several all-carbon tetrasubstituted alkenes, anticancer drug Tamoxifen, and AIEgen agent TPE-TF17.image