Janus POSS Based on Mixed [2:6] Octakis-Adduct Regioisomers

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. Two faces: A series of regioisomeric Janus polyhedral oligomeric silsesquioxanes with multiple, mixed surface functional groups at precise locations has been successfully prepared and was thoroughly characterized as a class of novel nano‐building blocks (see scheme; RA and RB=two different types of functional groups).