A throughway to functional poly(disubstituted acetylenes): a combination of the activated ester strategy with click reaction†
We report synthetic routes to functional poly(disubstituted acetylenes) (PDSAs) through the combination of the activated ester strategy and Cu(I) catalyzed azide–alkyne cycloaddition (CuAAC) reaction. Direct polymerization of a disubstituted acetylene monomer with an end-alkyne group under the catalysis of WCl6-Ph4Sn led to the poly(monosubstituted acetylene) by-product (P1) but not the expected PDSA bearing end-alkyne groups. Protection of the end-alkyne group could lead to the expected product but this route has low efficiency. Using the activated ester functionalized PDSA as a precursor (P0) and propargylamine as the modifier, the end-alkyne groups were easily attached onto the side chains of PDSA (P2). Based on the intermediate, the functional group could be efficiently modified onto the intermediate by reacting with azide containing reagents (using benzyl azide as a model) through the CuAAC click reaction, and finally the triazole functionalized PDSA (P3) was derived. The combination of the activated ester and the CuAAC click reaction strategy bestows the synthetic route with the advantages of high efficiency, mild reaction conditions and potentially plentiful functionalities (due to the versatile azide reagents).