Diorganyl Diselenides and Iron(III) Chloride Drive the Regio- and Stereoselectivity in the Selenation of Ynamides

Abstract

We report here our results on the application of ynamides as substrates in the reactions with diorganyl dichalcogenides and iron(III) chloride to give selectively three different types of compounds: E-αchloro-β-(organoselenyl)enamides, 4-(organochalcogenyl)oxazolones, and vinyl tosylates. The results reveal that the selectivity in the formation of products was obtained by controlling the functional groups directly bonded to the nitrogen atom of the ynamides. Thus, α-chloro-β-(organoselenyl) enamide derivatives were exclusively obtained when the TsN-and MsN-ynamides were treated with a mixture of diorganyl diselenides (1.0 equiv) and FeCl 3 (3.0 equiv) in dichloroethane (DCE, 3 mL), at room temperature. The 4-(organochalcogenyl)oxazolones were selectively obtained with ynamides having an ester group, directly bonded to the nitrogen atom, upon treatment with a solution of FeCl 3 (1.5 equiv) and diorganyl dichalcogenides (1.0 equiv) in dichloromethane (3 mL) at room temperature. Finally, vinyl tosylates were obtained from ynamides having an ester group, directly bonded to the nitrogen atom, by reaction with p-toluenesulfonic acid. We also studied the application of the prepared compounds as substrates for Suzuki and Sonogashira cross-coupling reactions.

Synthesis of 4-(organoselenyl) oxazolones via cyclization of N-alkynyl ethylcarbamates promoted by organoselenium

“…3-(4-Chlorophenyl)-5-phenyl-4-( phenylselanyl)oxazol-2(3H)-one (2e) 14 The product was isolated by column chromatography (hexane : ethyl acetate 95 : 5) as a white solid. Yield: 0.074 g (70%); mp 161-163 °C.…”

“…4,143.9,139.1,134.3,131.5 (q,J = 32.4 Hz),130.5,129.8,129.7,129.6,129.3,128.6,127.8 (q, J = 3.8 Hz), 127.7, 126.9, 126.0, 124.7 (q, J = 3. 4-(Butylselanyl)-5-phenyl-3-( p-tolyl)oxazol-2(3H)-one (2n) 14 The product was isolated by column chromatography (hexane : ethyl acetate 95 : 5) as a yellow solid. Yield: 0.059 g (61%); mp 69-71 °C.…”

“…13 In recent studies, we found that the reaction of ynamides with diorganyl dichalcogenides and iron( iii ) chloride preferentially gave E -α-chloro-β-(organoselenyl)enamides, the product of alkyne reduction, and 4-(organochalcogenyl)oxazolones. 14 For this reason, we have undertaken a study to promote the cyclization reaction under metal-free conditions, avoiding the addition of the electrophilic organoselenium species to the carbon–carbon triple bond.…”

α-Haloenamides: Synthesis and Subsequent Transformations

“…1)). 29 Although yields were lower than those obtained from the direct use of PhSeCl (or PhSeBr), a significant improvement in selectivity was observed by increasing the loading of iron(III) chloride up to 3 equiv. Under these conditions although enamides were formed in low to acceptable yields, but only (E)-isomers were isolated.…”

Methylselenized Glucose: Improvement of the Stability of Glucose-Supported Selenium via the End-Capping Strategy

“…Selenium (Se) is a necessary trace element for animals with unique bio- and chemical activities. − Investigations on the science of selenium involve multidisciplines and have recently attracted extensive interest because Se-containing compounds and materials are widely employed as building blocks in organic synthesis, − as catalysts in fine chemical production, − as bioactive components in pharmaceutical development, , as functional constituents in materials science, − and as fertilizers, feed additives, or pesticides in agricultural and food chemistry . In the field, glucose-supported selenium is a novel material with comprehensive applications.…”