|
Z. Naturforsch. 2013,
68b, 823 – 830
doi:10.5560/ZNB.2013-3036
Cyclocondensations of Substituted Thiosemicarbazides with 2-Bromo-1,2-diphenylethan-1-one
1 Institut für Biochemie, Universität Greifswald, Felix-Hausdorff-Str. 4, 17487 Greifswald, Germany
2 Scientific and Production Center “Armbiotechnology” of NAS RA, 14 Gyurjyan Str., 0056 Yerevan, Armenia
3 Department of Pharmaceutical Chemistry, Yerevan State University, Alex Manoogian Str. 1, 0025 Yerevan, Armenia
4 Institut für Chemie, Universität Rostock, Albert-Einstein-Str. 3a, 18059 Rostock, Germany
5 Leibniz-Institut für Katalyse e. V. an der Universität Rostock, Albert-Einstein-Str. 29a, 18059 Rostock, Germany
Reprint requests to Prof. Dr. Peter Langer. Fax: +381 4986412, E-mail:
peter.langer@uni-rostock.de
Received February 6, 2013 / published online July 19, 2013
The cyclocondensation of 4-methylthiosemicarbazide with 2-bromo-1,2-diphenylethan-1-one in ethanol afforded isomeric 2-methylamino-5,6-diphenyl-6H-3,4-thiadiazine and 2-hydrazono-3-methyl-4,5-diphenyl-2,3-dihydro-1,3-thiazole. A pyrazole was obtained by cyclocondensation and subsequent desulfurization of the thiadiazine when the reaction was carried out in concentrated hydrochloric acid. A chemical proof of the structures has been provided. The product distribution of the cyclizations strongly depends on the substitution pattern of the starting materials, and the cyclizations of methylthiosemicarbazide with 2-bromo-1,2-diphenylethan-1-one behaved considerably different from that of the analogous reactions of α-bromoacetophenone.
Key words: Cyclizations, Heterocycles, Thiadiazines, Regioselectivity, Thiazoles, Rearrangement