Shuai-Yuan Han, Xiao-Man Wang, Yu Shao, Qing-Yun Guo, Yiwen Li, Wen-Bin Zhang*. Janus POSS Based on Mixed [2:6] Octakis-adduct Regio-isomers. Chem. Eur. J. 2016, 22, 6397-6403. [Link] [PDF]


Abstract
A series of regioisomeric Janus-type polyhedral oligomeric silsesquioxanes (POSS) with multiple, mixed surface functional groups has been successfully synthesized based on the cubic T8-POSS framework in two consecutive thiol–ene reactions. The first thiol–ene addition of β-mercaptoethanol leads to a statistical mixture of multi-adducts where the regioisomers of bis-adducts (ortho, meta, and para isomers) can be isolated at synthetically useful quantities by flash column chromatography. Then, the second thiol–ene reaction readily installs a variety of functional groups onto the remaining vinyl groups of each regioisomer, providing an easy access to precisely defined, hetero-bifunctional Janus POSS nano-building blocks. The configurations and structures of the products have been unambiguously proven by using 1H, 13C, and 29Si NMR spectroscopy as well as MALDI-TOF mass spectrometry.