Controllable Si−C Bond Activation Enables Stereocontrol in the Palladium‐Catalyzed [4+2] Annulation of Cyclopropenes with Benzosilacyclobutanes

• Published in: Angewandte Chemie Vol. 132; no. 2; pp. 800 - 807
• Main Authors: Wang, Xing‐Ben, Zheng, Zhan‐Jiang, Xie, Jia‐Le, Gu, Xing‐Wei, Mu, Qiu‐Chao, Yin, Guan‐Wu, Ye, Fei, Xu, Zheng, Xu, Li‐Wen
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 07.01.2020
• Subjects: Activation; Chemical reactions; Chemistry; Enantiomers; Gespannte Moleküle; Heptanes; Organic chemistry; Organic compounds; Palladium; Ringaufweitung; Si-C-Bindungsaktivierung; Silacyclen; Stereoselectivity
• ISSN: 0044-8249; 1521-3757
• DOI: 10.1002/ange.201913060

A novel and unusual palladium‐catalyzed [4+2] annulation of cyclopropenes with benzosilacyclobutanes is reported. This reaction occurred through chemoselective Si−C(sp2) bond activation in synergy with ring expansion/insertion of cyclopropenes to form new C(sp2)−C(sp3) and Si−C(sp3) bonds. An array of previously elusive bicyclic skeleton with high strain, silabicyclo[4.1.0]heptanes, were formed in good yields with excellent diastereoselectivity under mild conditions. An asymmetric version of the reaction with a chiral phosphoramidite ligand furnished a variety of chiral bicyclic silaheterocycle derivatives with good enantioselectivity (up to 95.5:4.5 er). Owing to the mild reaction conditions, the good stereoselectivity profile, and the ready availability of the functionalized precursors, this process constitutes a useful and straightforward strategy for the synthesis of densely functionalized silacycles. Wenn Si−C auf C=C trifft: Cyclopropene wurden stereoselektiv mit Benzosilacyclobutanen durch Pd‐katalysierte Si‐C(sp2)‐Bindungsaktivierung und eine Ringerweiterung/[4+2]‐Anellierungssequenz funktionalisiert, um neue C(sp2)‐C(sp3)‐ und Si‐C(sp3)‐Bindungen von Silabicyclo[4.1.0]heptanen zu bilden. So wurde eine Reihe zuvor schwer herstellbarer, hochgespannter bicyclischer Gerüste in guten Ausbeuten mit hoher Selektivität erhalten (siehe Schema).