Benzoxazine-isonitrile Three-component Reaction And Its Application In Polymer Construction

As a new class of modified phenolic resin,benzoxazines are a type of oxygen and nitrogencontaining,six-membered heterocyclic compounds.Benzoxazines have attracted wide attention because of their excellent comprehensive properties,such as abundant starting substrates,high molecular-structure design flexibility,no catalyst required in the synthesis process,near-zero volumetric change and no release of toxic by-products during curing.However,despite the widespread investigation of benzoxazines as thermosetting plastics,scarce attention has been paid to the utilization of the chemical reactivity of the benzoxazine ring up to now.The deformed chair configuration results in a large ring strain for benzoxazines,and the methylene group(-CH2-)between N,O atoms is activated due to the connection with two electronegative atoms.Therefore,the high reactive imine intermediate might be formed by the ring-opening of benzoxazine under some conditions.It has been reported that that nucleophiles could promote the ring-opening of benzoxazines and induce the subsequent nucleophilic addition.Except for the benzoxazine-thiol reaction(COLBERT reaction)reported recently,to our knowledge,there is no report regarding the ring-opening addition reaction of benzoxazines with other nucleophiles.Hence,using benzoxazines as the reaction substrate to construct novel compounds have become a potential researching field.Isocyanides possess similar metal coordination capability and nucleophilicity with thiols,and play a vital role in organic syntheses as one of key substrates in multicomponent reactions.Nevertheless,the main obstacle for the application of isocyanides is their extremely unpleasant odor(for a majority of alkyl isocyanides).Although most of aromatic isocyanides are odorless,the chemical activity decreases due to the conjugation effect between isocyanides and aromatic rings.Thus,the investigation of new reactions based on odorless isocyanides could effectively expand its application prospects in synthetic chemistry.Based on this,we systematically investigated the reaction between benzoxazines and isocyanides,developing corresponding model reaction and its further application in polymer construction.The main work includes the following three parts:(1)Developed a novel three-component reaction with benzoxazines,odorless isocyanides,and water as the starting substrates.The reaction use octylphosphonic acid(OPA)as a catalyst and could efficiently afford amides at room temperature;(2)The corresponding three-component polymerization system had been developed with bifunctional benzoxazines and isocyanides as monomers.The results tells that this polymerization system showed the advantages of high reaction efficiency(6 h),mild reaction conditions(room temperature and metal-free catalyst)and wide substrate adaptability;(3)Functional isocyanides,which containing triphenylamine groups,was synthesized and polymerized with bifunctional benzoxazine to prepare an electrochromic polyamide,providing successful sample for the application of this polymerization system in construction of functional polymers.