S 98 Synthesis, Structure, and Keto-Enol Tautomerism of 3-R1-5,5-R2,R2-6-R3-2,3,5,6-Tetrahydropyran-2,4-diones [Electronic resource] / V. V. Shchepin, M. I. Kodess, Yu. Kh. Sazhneva, N. Yu. Russkikh // Russian Journal of General Chemistry. - 2005. - Vol. 75, № 10. - P1622-1627 Рубрики: ХИМИЧЕСКИЕ НАУКИ Аннотация: Ethyl esters of 2,4-dibromo-2-R1-4-R2-3-oxopentanoic and -hexanoic acids react with zinc and aliphatic or aromatic aldehydes under the conditions of the Reformatskii reaction to give 3-R1-5,5-R2, R2-6-R3-2,3,5,6-tetrahydropyran-2,4-diones, which are obtained in three forms: keto, enol with enolization of the keto group, and enol with enolization of the ester group. The keto form is isolated by crystallization from a mixture of CCl4 and petroleum ether; the first enol form, from MeOH, EtOH, and polar aprotic solvents; and the second enol form, from CHCl3. The second enol form is oxidized in DMSO to form a keto compound containing a hydroxy group at the 3-position of the heteroring \\\\Expert2\\nbo\\Russian Journal of General Chemistry\\2005, V. 75, N 10, p.1622.pdf |