Effects of the Herbicide Metolachlor and Pond Drying on Growth and Development of Wood Frog Tadpoles (Lithobates sylvaticus).

Pesticides and climate change are both thought to contribute to the global amphibian decline, yet their combined effects are still poorly understood. Metolachlor is a widespread herbicide applied across North America, but little is known about its effects on amphibians. We used a replicated mesocosm experimental design with different levels of drying (i.e., no drying and medium and rapid drying) and metolachlor concentrations (0, 0.8, 8, and 80 µg/L) to assess their respective and combined effects on wood frog (Lithobates sylvaticus) larvae throughout metamorphosis. Metolachlor had no significant effect on survival and development of tadpoles. However, metolachlor significantly interacted with drying levels to reduce the growth of tadpoles, which was mainly due to a difference detected among metolachlor concentrations under the rapid drying treatment. Drying also directly reduced growth and body mass at metamorphosis. Our results suggest that environmental stressors, such as drying, should be considered in toxicological experiments to provide relevant exposure conditions to pesticides for ephemeral pond species in the context of global climate change. Environ Toxicol Chem 2023;42:1772-1781. © 2023 SETAC.

Continuous Flow Synthesis and Purification of Aryldiazomethanes through Hydrazone Fragmentation.

Electron-rich diazo compounds, such as aryldiazomethanes, are powerful reagents for the synthesis of complex structures, but the risks associated with their toxicity and instability often limit their use. Flow chemistry techniques make these issues avoidable, as the hazardous intermediate can be used as it is produced, avoiding accumulation and handling. Unfortunately, the produced stream is often contaminated with other reagents and by-products, making it incompatible with many applications, especially in catalysis. Herein is reported a metal-free continuous flow method for the production of aryldiazomethane solutions in a non-coordinating solvent from easily prepared, bench-stable sulfonylhydrazones. All by-products are removed by an in-line aqueous wash, leaving a clean, base-free diazo stream. Three successful sensitive metal-catalyzed transformations demonstrated the value of the method.