Synthesis of Degradable Polyimines Through Deborylative Polycondensation

Polyimines are degradable and have found applications in separation techniques, gene delivery, optoelectronics, and porous materials. Conventional methods to synthesize polymines involve dehydrative polycondensation, which requires the addition of acid catalysts and drying reagents and has limited substrate scope. In this work, a boron-mediated strategy has been developed for the synthesis of polyimines. First, we describe the borylation of diamines at the nitrogen sites to afford N,N'-bis(boryl)diamines. Due to the N─B bond formation, N,N'-bis(boryl)diamines react fast, irreversibly, and completely with the dialdehydes via an unusual deborylative polycondensation process. Furthermore, methods for deborylative polycondensation reactions were developed under anhydrous and neutral conditions, yielding polyimines containing both aryl and alkyl backbones at room temperature in good to excellent yields. This polymerization protocol is scalable and reduces the operational difficulty in purifying the polyimines. These results provide a general and efficient polymerization tool for the practical synthesis of degradable polyimines.