Cu(I)-Catalyzed Heterogeneous Multicomponent Polymerizations of Alkynes, Sulfonyl Azides, and NH4Cl

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Nitrogen-containing polymers are a group of fascinating materials, which are usually prepared from nitrogen-containing organic monomers produced from NH₃ gas or aqueous solution of ammonia. The direct utilization of safe, clean, convenient, and inexpensive inorganic NH₄Cl salt as a nitrogen source for the construction of functional polymers is highly desired but challenging. Multicomponent polymerizations, with their strong designability, structural diversity, high efficiency, simple procedure, and environmental benefit, have been proven to be powerful tools to efficiently convert simple monomers to complex polymer materials. In this work, Cu(I)-catalyzed multicomponent polymerizations of alkynes, sulfonyl azides, and NH₄Cl are developed, utilizing simple inorganic NH₄Cl salt to serve as a monomer for the preparation of functional poly(sulfonyl amidine)s. The heterogeneous polymerization goes smoothly at room temperature in CH₂Cl₂/tetrahydrofuran, which is also applicable to a range of different monomer structures, affording seven poly(sulfonyl amidine)s with high yields (up to 96%) and high molecular weights (up to 47,100 g/mol). Unique functionalities such as photophysical properties and metal ion detection can be introduced to the poly(sulfonyl amidine)s either from monomer structures or the in situ generated product structures, rendering them as selective and sensitive fluorescence sensors for Ru³⁺. This multicomponent polymerization showed high synthetic efficiency with environmental and economic benefit, which has opened up a feasible synthetic method of using inorganic NH₄Cl salt instead of organic amines, isocyanates, isocyanides, or nitriles to construct nitrogen-containing polymers, demonstrating a promising synthetic approach for the synthesis of advanced functional polymer materials.