Metal‐Free Autoxidative Nitrooxylation of Alkenyl Oximes with Molecular Oxygen

Abstract

A metal‐free aerobic autoxidative nitrooxylation of alkenyl oximes mediated by tert‐butyl nitrite is described. Molecular oxygen is used as the oxidizing reagent, avoiding use of organic trapping reagents such as 2,2,6,6‐tetramethylpiperidine 1‐oxyl (TEMPO). The desired products were obtained in generally high yields.magnified image

Iminoxyl radicalsvs. tert-butylperoxyl radical in competitive oxidative C–O coupling with β-dicarbonyl compounds. Oxime ether formation prevails over Kharasch peroxidation

“…The proposed system is a convenient source of oxime radicals, which have found wide application in various processes of cyclization [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] and C-O coupling recently. 8,39 It should be noted that oxime radicals remain one of the least studied class of N- oxyl radicals, whereas amine-N-oxyl radicals and imide-N-oxyl radicals are used in numerous elds of chemistry, including oxidation methodology, [40][41][42] living radical polymerization, 40,43 spin-labeling, 44,45 organic magnetic materials design.…”

Recent Advances in Radical Dioxygenation of Olefins

“…[31] In this procedure, tBuONO serves as a dualfunction reagent: organic NO source as well as a radical initiator. Very recently, Wang and co-workers unveiled a tBuONO-mediated synthesis of nitrooxyisoxazolines with use of versatile alkenyl oximes and molecular oxygen as sole oxidizing agent (Scheme 35).…”

Ruthenium‐Catalyzed Direct Transformation of Alkenyl Oximes to 5‐Cyanated Isoxazolines: A Cascade Approach Based on Non‐Stabilized Radical Intermediate

“…We envisioned that, an efficient one‐step cyanation method could be developed if radical B could be selectively trapped by a nitroso radical or related species, followed by a successive tautomerization and dehydration (Scheme , bottom). Although trapping radical B with a nitroso radical (or related species), and forming the dimeric compound of C has been reported,[14e] tuning the reaction to the desired cascade reaction pathway is still a difficult job, given the fact that the primary carbon radical B is extremely reactive (it reacts with air even at low temperature), and intermediate C is prior to dimerization. [14e] The identification of regents compatible with the radical conditions, and capable of converting the oxime D to a nitrile is another daunting task.…”