A New Environmentally Friendly Approach to Lignin‐Based Cyclic Carbonates. Issue 7 (30th January 2018) - Kühnel, Isabell
Abstract: Herein, a novel synthesis of a fully renewable lignin‐based building block equipped with cyclic carbonate functionalities is presented. In an efficient two‐step procedure, organosolv lignin from ethanol–water pulping of beech wood is oxyalkylated with glycerol carbonate to insert adjacent hydroxyl groups. The oxyalkylated lignin is then reacted via transesterification with dimethyl carbonate or ethylene carbonate in dimethyl sulfoxide under alkaline conditions producing cyclic carbonate functionalized lignin. This transesterification is studied as a function of time, catalyst type, and catalyst amount using NMR spectroscopy as well as size exclusion chromatography. Transesterification reactions with K2 CO3 as catalyst (0.4 eq.) afford lignin‐based cyclic carbonate with almost complete conversion (96%) within 6 h, as analyzed by 31 P and 13 C NMR spectroscopy. This green building block represents a reactive prepolymer for the synthesis of nonisocyanate polyurethanes. Abstract : Cyclic‐carbonate‐functionalized lignin is obtained via a straightforward, environmentally friendly approach. This two‐step procedure using organosolv lignin from ethanol–water pulping of beech wood allows the synthesis of a renewable prepolymer for the synthesis of nonisocyanate polyurethanes.