Ultrasound and Oxone® promoting regioselective selenofunctionalization of chromone

Abstract

Selective, simple and green synthetic procedures constitute an important goal in organic synthesis. In this sense, we describe the synthesis of 3-(organylselanyl)-4H-chromen-4-ones by regioselective selenofunctionalization of the chromone core using diorganyl diselenides. These reactions were efficiently conducted under mild conditions, employing Oxone® as stable and non-hazardous oxidizing agent in the presence of ultrasound in short reaction times. By this efficient approach, new eight compounds were obtained in moderate to excellent yields.

Ag(i)-catalyzed three-component radical cascade synthesis of 3-organoselenyl chromones from 2-methoxyaryl alkynones, Se powder and organic boronic acids

“…The second one was the electrophilic cascade cyclization of 2-hydroxyaryl enaminones with organoselenium cations, which were in situ generated either from RSeCl and AgOTf, 10 or from RSeSeR by oxidation with TCCA, 11 or by air under the catalysis of KNO 3 12 or light irradiation 13 (Scheme 1b). The last one was the direct selenylation of preformed chromone rings with organoselenium radicals or anions, derived from RSeSeR, 14 sodium seleninate, 15 KSeCN/ArI, 16 or Se powder/ArI, 17 via various oxidative or Cu-catalyzed C–H bond active strategies (Scheme 1c). Other than these, the first approach provided 2-substituted 3-organoselenyl chromones, while the latter two approaches generated 2-unsubstituted 3-organoselenyl chromones.…”

Radical cyclization of alkynyl aryl ketones for the synthesis of 3-seleno-substituted thiochromones and chromones

“…In this sense, some new protocols have been developed to prepare 3-selanyl-functionalized chromones and thiochromones. 16 Among them, the electrophilic cyclization reaction between alkynyl aryl ketones and electrophilic selenium species is the most explored approach. For instance, in 2011, Zeni and co-workers 17 reported the synthesis of a variety of 3-organoselanylchromones by the cyclization reaction of 1-(2-methoxyphenyl)-3-arylprop-2-yn-1-ones promoted by FeCl 3 /(PhSe) 2 in dichloromethane (Scheme 1A).…”

Regioselective peri-C–H selenylation of aromatic compounds with weakly coordinating ketone groups

“…In recent years, several protocols have been developed for direct selenylation of chromones at the C3-position, and 3-selenyl chromones were formed by the electrophilic attack of the selenium species to the C3-position of the chromones (Scheme 1a). 4 In sharp contrast, no methods have been reported for the preparation of 5-selenyl chromones. As part of our ongoing studies on the development of efficient routes for the preparation of functionalized heterocyclic compounds, 5 we are interested in the exploration of novel methods for the synthesis of 5-selenyl chromones via direct selenylation of chromones at the C5-position.…”

“…Diselenides can be easily converted to selenyl cations or radicals, and many metal-catalyzed selenylation reactions involve selenyl cations or radicals, 8 which can readily attack the C3-position of chromones due to their strong nucleophilicity. 4 So, the biggest challenge of this strategy is the discrimination of the C3- and C5-positions for the regioselective synthesis of 5-selenyl chromones (Scheme 1b). We herein present a Ru( ii )-catalyzed novel protocol for the regioselective C–H selenylation of chromones at the C5-position with diselenides.…”