Synthesis of Furoxans (1,2,5‐oxadiazole 2‐oxides) from Styrenes and Nitrosonium Tetrafluoroborate in Non‐Acidic Media and Mechanistic Study

Abstract

Diverse furoxans (1,2,5‐oxadiazole 2‐oxides) were synthesized from the corresponding styrenes using nitrosonium tetrafluoroborate as the nitrosation reagent in pyridine (basic media) or dichloromethane (neutral media). Acid‐sensitive functional groups were tolerated under these conditions. The probable reaction mechanism was elucidated. The experimental results support an ionic reaction pathway in contrast to the conventional acidic conditions with a radical mechanism.

Reactive nitrogen species: Nitrosonium ions in organic synthesis

“…Intermediate 38B reacts with a second equivalent of the nitrosonium ion to form 38C, which undergoes ring closure to form furoxanes 39. [42] The same results were achieved using the NaNO 2 -AcOH system. [43] Wu and co-workers contributed with an interesting example of a radical annulation reaction of imines (40) with electron-rich alkenes (41) (Scheme 14).…”