S 98 Synthesis of 4-(thien-2-yl)-substituted coumarins through Lewis acid catalyzed Michael addition of thiophenes to 3-benzoylcoumarins followed by oxidation [Electronic resource] / R. A. Irgashev, A. A. Karmatsky, G. L. Rusinov, V. N. Charushin // Tetrahedron Letters. - 2014. - Vol.55, №26. - С. 3603-3606 Рубрики: ХИМИЧЕСКИЕ НАУКИ Кл.слова (ненормированные): THIOPHENES -- 3-BENZOYLCOUMARINS -- Lewis acid Аннотация: 3-Benzoyl-4-(thien-2-yl)coumarins have been obtained in good yields according to the SNH addition–oxidation protocol, involving the diastereoselective addition of thiophenes at C-4 of 3-benzoylcoumarins under BBr3 catalysis, followed by oxidation of the intermediate 3,4-trans-3-benzoyl-4-(thien-2-yl)-3,4-dihydrocoumarins with DDQ. This two-step procedure can be regarded as nucleophilic substitution of hydrogen (SNH) on the heterocyclic ring of coumarins \\\\expert2\\nbo\\Tetrahedron Letters\\2014, v. 55, p. 3603.pdf |