Quantitative Benchmarking of Ritter Amidation: A Sustainability Perspective Inspired by Roger A. Sheldon

Roger A. Sheldon transformed Green Chemistry by demonstrating that the sustainability of chemical processes should be evaluated through objective quantitative metrics rather than qualitative claims of “greenness”. Building on this philosophy, this perspective benchmarks representative Ritter amidation methodologies using harmonized reaction-level boundaries and complementary green chemistry metrics, including carbon efficiency (CE), reaction mass efficiency (RME), process mass intensity (PMI), complete and simplified E-factors (sE-factor), solvent intensity (SI), and EcoScale. The comparison demonstrates that catalyst innovation and high isolated yield do not necessarily translate into improved sustainability. Instead, material consumption, particularly excess nitrile, reaction-medium demand, and downstream processing, dominates the environmental profile of most methodologies. At the reaction level, and within the benzamide series, solvent-free Ritter amidation provides the most favorable balance between synthetic performance and material efficiency; scale-up readiness is discussed qualitatively.