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

Abstract

NO2 is an effective catalyst for the oxidative thiocyanation of arenes. This unique catalyst is inexpensive and separated easily from the final products because of its low boiling point. The mild reaction conditions allow a series of arenes and thiophenes to be thiocyanated smoothly in moderate to high yields. A preliminary mechanistic investigation suggests that the present reaction may proceed through a radical pathway.

Sustainable Synthetic Approaches Involving Thiocyanation and Sulfur- Cyanation: An Update

“…In the oxidative thiocyanation of various aromatic compounds (1) with ammonium thiocyanate, with air used as the oxidant, NO 2 was added as a new catalyst, inexpensive and easy to separate from the final products [2]. The reaction was compatible with various electron-donating or electronwithdrawing substituents present on the aromatic ring, leading to the corresponding thiocyanates (2) in moderate to high yields (Scheme 2). The authors proposed the NO + species as the reaction catalyst, which is generated from NO 2 .…”

Reactive nitrogen species: Nitrosonium ions in organic synthesis

“…Later, the same group expanded the developed reaction to the oxidative thiocyanation of electron-rich arenes 65 by employing gaseous nitrogen dioxide as the catalyst (Scheme 26). [72] The reaction proceeds through generation of a radical cation intermediate, which reacts with the thiocyanate. Subsequent oxidation and rearomatization affords the corresponding arylthiocyanate 66.…”

Direct Photocatalytic S–H Bond Cyanation with Green “CN” Source

“…Thiocyanates are usually served as the synthetic precursors for the assembly of trifluoromethyl sulfides, sulfonyl chlorides, thiols, thiocarbamates, heterocycles, disulfides, thioethers and so on, which have prompted the requirement of development of efficient synthetic strategies. Although significant efforts have been achieved in the thiocyanation in the past few years, the preparation of thiocyanates focused mainly on the two fashions (Scheme ): (1) the transformation of a substrate bearing an nucleophilic or electrophilic sulfur with a cyanating agent (path 1); − and (2) the reaction of various sulfur-free alkyl/aryl substrates with a thiocyanating agent (path 2). , However, most of the above-mentioned procedures suffer from some drawbacks such as requiring transition metals, ligands, oxidants, abnormal temperatures, or using unavailable, high cost, especially high toxicity “CN” sources (CuCN). Thus, the acquisitions of nontoxic, inexpensive and green “CN” sources for the thiocyanation under mild conditions have been attracting the attention of organic and pharmaceutical chemists.…”