Nitrogen Dioxide‐Catalyzed Electrophilic Iodination of Arenes

Abstract

Nitrogen dioxide is demonstrated to be an effective catalyst precursor for the iodination of alkoxy-substituted benzenes and naphthalenes. Different from the transition metal catalysts, nitrogen dioxide can be easily separated from the final products, and is free of heavy metal waste. Although the present catalyst precursor is toxic, it does not stain the final products due to its low-boiling character. No other reagents apart from 0.5 equiv. of iodine (I 2 ), 6.5 mol% nitrogen dioxide and acetonitrile solvent were used in the iodination, and basically all the iodine atoms in the iodine source were transferred to the iodination products, showing that the presented protocol is highly atom-economic and practical.

Nitrogen Dioxide Catalyzed Oxidative Thiocyanation of Arenes with Ambient Air as the Terminal Oxidant

“…Encouraged by our previous success in the application of NO 2 to catalyze aerobic oxidative halogenation, we selected this readily available compound as the catalyst to initiate our investigation. The catalytic ability of NO 2 was very poor if 1‐alkoxynaphthalene was stirred with ammonium thiocyanate in acetonitrile in the presence of catalytic NO 2 at 15 °C (Table , entry 1).…”

“…Subsequently, we tried to ascertain the real catalytic species. It is known that NO 2 is an effective catalyst for the activation of O 2 . Indeed, oxidative thiocyanation did not occur in the absence of a catalytic amount of NO 2 .…”

“…Encouraged by our previous success in the applicationo fN O 2 to catalyze aerobic oxidative halogenation, [16] we selected this readily available compound as the catalystt oinitiate our inves-NO 2 is an effective catalyst for the oxidative thiocyanation of arenes. This unique catalyst is inexpensive ands eparated easily from the final products because of its low boiling point.…”

“…Amongt he test alkoxybenzenes, 1,2,3-trimethoxybenzene was thiocyanated smoothly to give the thiocyanation product in ah ighy ield ( Table 2, entry 6), but it is difficult to understand why methoxybenzene was unreactive. Next, N,N-dimethylanilines with various substituents were used as the substrates to investigate the electronic and steric effectso ft he substituents on the reaction ( Table 2, entries [8][9][10][11][12][13][14][15][16][17]. Generally, N,N-dimethylanilines with electron-donatingo r -withdrawing groups could be used successfully in this system.…”

“…It is known that NO 2 is an effective catalystf or the activation [c] 97 90 22 70 -23 [c] 89 76 24 [d] 87 - ChemCatChem 2016, 8,3361 -3366 www.chemcatchem.org of O 2 . [16] Indeed, oxidative thiocyanation did not occur in the absence of ac atalytic amount of NO 2 .T his suggests that the real catalytic speciesc omesf rom NO 2 .T his compound or its dimer can be decomposedt og ive NO + + in dilute solutions of strong acid, [17c, 20] thus NO + + seems to be one of the real catalytic species. [21] Indeed, the use of NO + + allowed N,N-dimethylaniline to undergo thiocyanation smoothly with ah igh product yield of 92 %(Scheme 4).…”