- Nonselective bromination-selective debromination strategy: Selective bromination of unsymmetrical ketones on singly activated carbon against doubly activated carbon
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(Matrix presented) We have found a new synthetic method for the preparation of the α-bromoketones that are brominated in the less activated terminal position of unsymmetrical ketones. Brominations in short reaction times (kinetically controlled) provided internally brominated compounds as a major product. However, brominations in longer reaction times (thermodynamically controlled) gave more of the terminally brominated compound through the reversible reaction by Br2 and produced hydrogen bromide. Several brominated compounds at the terminal position were successfully prepared through the new synthetic route.
- Choi, Han Young,Chi, Dae Yoon
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p. 411 - 414
(2007/10/03)
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- Condensed pyridine bases. A new approach to the synthesis of 3-phenacylbenzo[b]thiophenes and 3-phenacyl-5-ethyl-thieno[2,3-b]thiophene. Synthesis of new derivatives of benzothieno[2,3-c]pyrylium and thieno[2′,3′:5,4]thieno-[2,3-c]pyrylium and pyridine bases
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A new method is proposed for the production of substituted 3-phenacylbenzo[b]thiophenes by the intramolecular cyclization of 1-phenyl-4-phenylthio-1,3-butanediones in polyphosphoric acid. The analogous cyclization of 1-phenyl-4-(5-ethyl-2-thienylthio)-1,3-butanedione leads to 3-phenacyl-5-ethylthieno[2,3-b]thiophene. The acylation of substituted 3-phenacylbenzo[b]thiophenes and 3-phenacyl-5-ethylthieno[2,3-b]thiophene by the anhydrides of aliphatic acids in the presence of perchloric acid leads to 1-alkyl-3-phenylbenzothieno[2,3-c]pyrylium perchlorates and 2-ethyl-5-phenyl-7-methylthieno[2′,3′:5,4]thieno[2,3-c]pyrylium perchlorate. The action of ammonium acetate on the obtained salts gives the corresponding pyridine bases. 1999 Kluwer Academic/Plenum Publishers.
- Tolkunov
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p. 1132 - 1136
(2007/10/03)
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