- Two-Step One-Pot Synthesis of Unsymmetrical (Hetero)Aryl 1,2-Diketones by Addition-Oxygenation of Potassium Aryltrifluoroborates to (Hetero)Arylacetonitriles
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An efficient one-pot two-step procedure for the synthesis of unsymmetrical (hetero)aryl 1,2-diketones has been developed. The reaction proceeds through a palladium-catalyzed nucleophilic addition of potassium aryltrifluoroborates to aliphatic nitriles followed by a copper-catalyzed aerobic benzylic C–H oxygenation using molecular oxygen as a green oxidant. This represents the first example of the direct synthesis of unsymmetrical diaryl 1,2-diketones from arylacetonitriles. This method utilizes inexpensive, stable, nontoxic, and readily available starting materials, is highly effective in the presence of both electron-rich and electron-poor nitriles and aryltrifluoroborates, and tolerates a wide variety of functional groups. The synthetic utility of this transformation was shown by increasing the scale of the reaction and by carrying out the one-pot protocol for the preparation of quinoxaline and benzimidazole derivatives. A plausible reaction mechanism has also been proposed.
- Kumar, Yogesh,Jaiswal, Yogesh,Kumar, Amit
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p. 494 - 505
(2018/02/09)
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- Synthesis of Thieno and pyrroles
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A simple and useful synthesis of thienopyrrole (1) and thienopyrrole (2) is reported. 2-Acetylthiophene (8) on bromination using iron/bromine affords 2-bromoacetylthiophene (9) which on treatment with sodium azide in aqueous ethanol at 0 deg C furnishes 2-azidoacetylthiophene (10). 10 on reduction with sodium borohydride in 95percent ethanol at room temperature furnishes 1-(2-thienyl)-2-azidoethanol (11) which on dehydration with methanesulphonyl chloride and dry pyridine in dry dimethylformamide affords 2-(ω-azidovinyl)-thiophene (12).Thermolysis of 12 in re-fluxing xylene furnishes the thienopyrrole (2).By a similar sequence of reactions thienopyrrole (1) is prepared starting from 3-acetylthiophene.
- Kumar, G.,Rajagopalan, K.,Swaminathan, S.,Balasubramanian, K. K.
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p. 271 - 274
(2007/10/02)
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