Janus ring siloxanes: versatile precursors of extended Janus ring and laddersiloxanes

All-cis-tetrasiloxycyclotetrasiloxanes (Janus ring siloxanes) were facilely prepared from cyclotetrasiloxanetetraol or potassium cyclotetrasiloxane silanolates. Further, we demonstrate the synthesis of an extended Janus ring, [RSi(OR’)O]4, containing various functional groups, via the Piers-Rubinsztajn reaction using the Janus ring siloxanes as a precursor. Remarkably, we discovered the formation of unexpected laddersiloxanes as a byproduct. These products were potential monomers of well-defined cage silsesquioxanes, Janus-type nanomaterials, and porous materials.