The importance of asymmetric organocatalysis in contemporary organic synthesis is widely acknowledged. However, there are practically no data on the environmental safety of organocatalysts, although this aspect is crucial for the sustainability of all new materials/chemicals/technologies. To start to fill this data-gap, a library of 26 organocatalysts containing hydrogen bonding catalysts ((thio)ureas and squaramides) and aminocatalysts (primary or secondary amines) was evaluated for their toxicity using the naturally luminescent Vibrio fischeri bacteria (an ISO assay – one of the most widely used ecotoxicity tests). We showed that thioureas and squaramides were relatively toxic: none of them was ranked as “not harmful” (i.e. EC 50 >100 mg/L) whereas the presence of the trifluoromethyl moiety increased their toxic effect. Importantly, the aminocatalysts whose EC 50 values ranged from 25 to >300 mg/L could be considered remarkably more environmentally safe or green alternatives.
Authors: Mariliis Sihtmäe, Estelle Silm, Kadri Kriis, Anne Kahru, Tõnis Kanger
; Full Source: ChemSusChem 2022 Jun 10. doi: 10.1002/cssc.202201045.