Highly selective scalable electrosynthesis of 4-hydroxybenzo[e]-1,2,4-thiadiazine-1,1-dioxides

Simple electrochemical synthesis of cyclic hydroxamic acids by reduction of nitroarenes

“…The acids 4a and 4c showed a broad reductive wave (−1.00 V vs. FcH/FcH + ) relating to the 4e − /4H + reduction of the nitroarene to the intermediary formed hydroxylamine, which is reported in the literature (Scheme 4). 15,17,18 Interestingly, only 4a showed a weak oxidative wave (+0.41 V vs. FcH/FcH + ) related to the reoxidation of the hydroxylamine to the nitroso arene. The 4-hydroxy-1,4-benzoxazin-3-ones 5a and 5c both showed two oxidative waves, which correspond to a N–O radical formed, which might later be oxidized to a cation.…”

“…14,15 Based on previous work on the direct electrochemical reductive synthesis of N–O heterocycles, a synthetic protocol for the selective and scalable synthesis of 2 H ,4 H -4-hydroxy-1,4-benzoxazin-3-ones was established, providing direct access to this highly promising class of compounds. 16–19…”