Preparation of 5‐bromo‐6‐phenylimidazo[2,1‐b][1,3,4]thiadiazol‐2‐ylamines

Abstract

The reaction of primary or secondary amines with 2,5-dibromo-6-phenylimidazo[2,1-b][1,3,4]-thiadiazole (5) leads to a chemoselective replacement of the 2-Br substituent. The process represents a convenient route to the corresponding 2-ylamines 7a-d. Hydrazine reacts in an analogous fashion (5 7e). The structure determinations are based on an X-ray crystal structure analysis and on one-and two-dimensional NMR measurements.

Synthesis of 2,6‐Disubstituted Imidazo[2,1‐b][1,3,4]thiadiazoles through Cyclization and Suzuki–Miyaura Cross‐Coupling Reactions

“…The presence of substituent in the ortho position of the aryl group lowered the yields, probably because of steric hindrance ( Table 1, Entries 3 and 7). In order to have a representative E library, methyl, ethyl ester, and 4-pyridinyl α-bromo ketones were additionally treated with 1 to afford desired products 2, 14, and 15 in only 20, 31, and 29 % yield, respectively (Table 1, Entries 1,13,14). The instability of these α-halogeno ketone derivatives could explain the lack of reactivity.…”

SNAr versus Buchwald–Hartwig Amination/Amidation in the Imidazo[2,1‐b][1,3,4]thiadiazole Series

“…Under the reported conditions (Table 1), which use an excess amount of morpholine in a solvent, the desired product 2 was obtained in very low yield. [29][30][31] Although the insolubility of starting material 1 was detrimental to the classical addition/elimination cascade reaction (Table 1, Entries 1 and 2), the yield could be enhanced by performing the reaction without a solvent. This assay afforded compound 2 in 83 % yield (Table 1, Entry 3).…”

Synthesis of 1,3,4-Thiadiazolo[2′,3′:2,3]imidazo[4,5-b]indoles

“…Imidazo 3), containing an obromophenyl group, was synthesised, by analogy with the protocol of a related reaction, 11 by cyclocondensation of 2,2′-dibromoacetophenone (2) with commercially available 2-aminothiadiazole (1, Scheme 1). 12,13 Subsequent bromination of 3 gave product 4.…”