- Ammonium Chloride-Promoted Rapid Synthesis of Monosubstituted Ureas under Microwave Irradiation
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Monosubstituted ureas are important scaffolds in organic chemistry. They appear in various biologically active compounds and serve as versatile precursors in synthesis. Monosubstituted ureas were originally prepared using toxic and hazardous phosgene equivalents. Modern methods include transamidation of urea and nucleophilic addition to cyanate salts, both of which suffer from a narrow substrate scope due to the need for a strong acid and prolonged reaction times. We hereby report that ammonium chloride can promote the reaction between amines and potassium cyanate to generate monosubstituted ureas in water. This method proceeds rapidly under microwave irradiation and tolerates a broad range of functional groups. Unlike previous strategies, it is compatible with other nucleophiles, acid-labile moieties, and most of the common protecting groups. The products precipitate out of solution, allowing facile isolation without column chromatography.
- Lan, Chunling Blue,Auclair, Karine
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supporting information
p. 5135 - 5146
(2021/10/19)
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- Hybrid calix[4]arenes via ionic hydrogenation and transition-metal-mediated processes
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We report the first application of ionic hydrogenation for the synthesis of upper-rim urea- or carbamate-derived hybrid calix[4]arenes. Subsequent metal-mediated transformations using 4-iodophenylurea calixarenes afforded structurally unique 1,3-di(biaryl)-, 1,3-di(biarylalkyne)-, or 1,3-(biaryl)(biarylalkyne)-derived hybrid calixarenes.
- Bew, Sean P.,Brimage, Rebecca A.,Hiatt-Gipson, Glyn,Sharma, Sunil V.,Thurston, Sean
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supporting information; experimental part
p. 2483 - 2486
(2009/10/18)
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