Synthesis and alkaline hydrolysis of (pentafluoroethyl)imidazoles |
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Institution: | 1. Nano Science and Technology Institute, University of Science and Technology of China, Suzhou 215123, PR China;2. School of Pharmacy & Pharmaceutical Sciences, Anhui University of Traditional Chinese Medicine, Hefei 230038, PR China;3. Department of Chemistry, CAS Key Laboratory of Soft Matter Chemistry, University of Science and Technology of China, Hefei 230026, PR China |
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Abstract: | Photochemical ring substitution of the N-trifluoroacetyl derivatives of histamine and of L-histidine methyl ester by pentafluoroethyl radical provides the corresponding 2- and 4-pentafluoroethylated products in yields of 19% and 27%, respectively. Alkaline hydrolysis converts the 2-pentafluoroethyl group to trifluoroacetyl. The reaction mechanism, involving a diazafulvene intermediate, is analogous to that elucidated for (trifluoromethyl)imidazoles; however, the pentafluoroethyl group is markedly more reactive to hydrolysis than the trifluoromethyl group. For imidazole derivatives, the ratio of reactivities is 75 at C-2 and 40 at C-4. The hydrolysis of 4-(pentafluoroethyl)histamine affords the bicyclic product, 4-(trifluoromethyl)-6,7-dihydro-1H-imidazo4,5-c]-pyridine in 65.4% yield. |
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