A comparative approach to the most sustainable protocol for the β-azidation of α,β-unsaturated ketones and acids†
In this contribution we have used green metrics analysis to compare the material efficiency, environmental impact, and safety-hazard impact in order to compare flow and batch procedures for azidation of α,β-unsaturated carbonyls. It has been proved that flow protocols possess a greener profile over the corresponding batch procedures based on identical chemistries. In this work the new flow procedure described is very efficient; however, the significant uncertainties in the environmental and safety-hazard impact scores are due to the lack of toxicity, hazard, and occupational exposure data available on trimethylsilyl azide and the resin catalysts used here. The results for the new flow procedure show significant and definite improvements over previously published work with respect to waste minimization/material efficiency and are consistent with satisfying green chemistry principles. The results obtained in this work prove the usefulness of our flow-approach for realizing highly efficient processes featuring minimal waste production.