Taming Cr(VI) Toxicity in Telescoping Quinoxaline Synthesis

Abstract We introduce a method to transform toxic hexavalent chromium (Cr(VI)) into bio‐compatible trivalent chromium (Cr(III)) during quinoxaline synthesis from alkynes or alkenes. Using H5IO6 as a co‐oxidant, this process addresses environmental and safety concerns associated with Cr(VI). The telescoping synthesis involves the rapid formation of 1,2‐diketones from internal alkynes or alkenes using catalytic CrO3 and H5IO6 in acetonitrile at room temperature. Adding o‐aryl diamine in isopropanol completes the reaction, with the solvent quenching the chromium oxidation state and aiding quinoxaline formation. This method yields high efficiency, broad substrate scope, and excellent selectivity, offering an eco‐friendly pathway for quinoxaline production while reducing Cr(VI) toxicity.