Influence of the structures of α-halo ketones and thioamides on the Hantzsch synthesis of thiazoles and thiazolo[5,4-b]indoles. A new approach to 4-acetyl-2-methyl-4H-thiazolo[5,4-b]indole
作者:A. Yu. Lepeshkin、K. F. Turchin、A. L. Sedov、V. S. Velezheva
DOI:10.1007/s11172-007-0219-5
日期:2007.7
into thiazoles (the expected Hantzsch reaction products). To the contrary, thiazoles are produced in the reactions of the same α-halo ketones with thioamides of phenylacetic, diphenylacetic, 3-indolylacetic, or cyanoacetic acids. The abnormal course of the Hantzsch reaction in the former case results from the fact that 4-hydroxy-Δ2-thiazolines, which are intermediates in the thiazolesynthesis, undergo
Mechanism of dehydration of 2-CH2R-and 2-CHR2-4-hydroxy-Δ2-thiazolines as intermediates in the Hantzsch thiazole synthesis and factors impeding the synthesis of 2-Me-, 2-Ar-, and 2-Het-substituted thiazoles and thiazolo[5,4-b]indoles
作者:A. Yu. Lepeshkin、K. F. Turchin、E. G. Gal’pern、I. V. Stankevich、K. A. Lyssenko、V. S. Velezheva
DOI:10.1007/s11172-007-0220-z
日期:2007.7
formation of the corresponding Δ3-thiazolines. According to the results of quantum chemical calculations, this is energetically more favorable than the dehydration in terms of the commonly accepted mechanism. In some cases, an acidic medium impedes the dehydration of 4-hydroxy-Δ2-thiazolines or their cyclic analogs. The proposed mechanism provides an explanation for the empirical data on the differences in