Phosphazene-Promoted Metal-Free Ring-Opening Polymerization of 1,2-Epoxybutane Initiated by Secondary Amides

The in situ generation of an anionic initiator X- obtained by the deprotonation of various secondary amides with tBuP(4) phosphazene base was tested as possible way to initiate the polymerization of 1,2-epoxybutane. The initiation efficiency of different amide-containing molecules was investigated. Particular attention was given to the detection of eventual transfer or side reactions, especially due to nucleophilic attacks on the initiator moiety at the alpha-chain end. In all cases, the initiation of the polymerization by the amidate anion was effective. And in most cases, the polymerization proceeded in a controlled manner to afford amide end-capped poly(butylene oxide) with narrow molar mass distribution and expected molar masses.