Self-Assembled Polymeric Pyridine Copper Catalysts for Huisgen Cycloaddition with Alkynes and Acetylene Gas: Application in Synthesis of Tazobactam

Novel convoluted polymeric pyridine copper­(I) catalysts PVPy-Cu were developed for the Huisgen cyclization of organic azides using alkynes and acetylene gas. They were readily prepared based on our molecular convolution of CuSO4·5H2O and poly­(4-vinylpyridine) (PVPy) in the presence of sodium ascorbate with and without various sodium salts in water. Their structural investigation was conducted using XANES and EXAFS, as well as DFT calculation. The Huisgen cycloaddition of a variety of alkynes and acetylene gas was carried out using 100 to 800 mol ppm of Cu of PVPy-Cu in water, whose turnover numbers reached up to 10 000. This catalytic system was applied to the synthesis of tazobactam, which is an inhibitor of bacterial β-lactamases.