Efficient synthesis of chitosan derivatives as clickable tools

•Efficient synthesis of alkynoyl chitosan derivatives having different spacers.•Direct N-modification of chitosan with good control of substitution.•N-alkynoyl chitosan derivatives as useful precursors to click chemistry.•Successful CuAAC reactions between alkynoyl chitosan and aromatic/PEG-azides.•Synthesis of 12 new chitosan based conjugates using click reaction.