A reusable polymer supported catalyst for copper-azide-alkyne cycloaddition (CuAAC) under ambient conditions

A novel recyclable polymer-supported copper(ii) catalyst [mPAN-Cu(ii)] is developed for the azide-alkyne 'click' reaction (CuAAC) under ambient conditions. mPAN-Cu(ii) can be easily prepared by immobilizing copper chloride over suitably functionalized polyacrylonitrile (mPAN). After detailed spectroscopic characterization, the catalytic efficacy of mPAN-Cu(ii) has been successfully explored for a one-pot, three-component Click reaction involving benzylbromide, sodium azide and phenyl acetylenes under mild conditions. Systematic optimization studies offered a more efficient and sustainable reaction protocol in the presence of sodium ascorbate, leading to the regioselective formation of 1,4-disubstituted 1,2,3-triazoles. This greener protocol was found to be general over a series of substrates, and the resulting products were isolated with good to excellent yields. Moreover, this catalyst can be easily recovered after the reaction and reused for up to six cycles without much drop in catalytic performance. Studies towards the development of an efficient heterogeneous catalyst for the copper-azide-alkyne cycloaddition (CuAAC) under ambient conditions are described.