One-Pot Multicomponent Tandem Reactions and Polymerizations for Step-Economic Synthesis of Structure-Controlled Pyrimidine Derivatives and Poly(pyrimidine)s

The development of new polymerization methodologies for the construction of π-conjugated polymers with unique electronic and photophysical properties is of great importance. Multicomponent tandem polymerizations (MCTPs), featured with high synthetic efficiency and convenience, have proved their potential in the synthesis of polymers with π-conjugated structures. Herein, a new multicomponent tandem reaction of alkyne, guanidine hydrochloride, DMSO, and O2 was reported through the combination of four sequential Glaser coupling–nucleophilic addition–heterocyclization–oxidation reactions in a one-pot procedure. The corresponding MCTP of diyne, guanidine hydrochloride, DMSO, and O2 was also developed in the presence of CuCl, N,N,N′,N′-tetramethylethylenediamine, and Cs2CO3 to afford conjugated poly(pyrimidine) with well-defined structure, high yield of 87%, and high molecular weight of 25300 g/mol. A mechanistic study of the reaction and a kinetic study of the polymerization were conducted, enabling facile modulation of polymer mainchain structure from rigid conjugated backbone to flexible nonconjugated backbone by simply tuning the atmosphere of the MCTP from air to nitrogen. The poly(pyrimidine)s enjoy outstanding thermal stability and good solubility, whose hydrophobicity and photophysical property are influenced by their subtle structural difference. This MCTP directly converts monomers with simple structure to complex heterocycle-containing products in a step-economic manner and constructs new functional substituted pyrimidine rings embedded in the polymer main chain, providing a compact approach for the efficient and convenient synthesis of structurally controllable poly(heterocycle)s and the construction of polymer materials with potential high-tech applications.