3,4-Dimethyl-2,5-functionalized thieno[2,3-b]thiophenes: versatile precursors for novel bis-thiazoles

Abstract

Synthesis of novel bis(thiazoles) 19–22, 24, 25, 30 and 31 is reported. Thus, reaction of the bis(α-bromoketones) 14 and 15 with the corresponding thioamide derivatives 16–18 in refluxing EtOH in the presence of triethylamine afforded 19–22 in good yields. On the other hand, the novel bis(thiazoles) 24 and 25 can be synthesized by the reaction of 14 and 15 with the corresponding p-chlorobenzaldehyde thiosemicarbazones 23 in refluxing EtOH. The novel isomeric bis(thiazoles) 30 and 31 can also be synthesized by a reaction of the corresponding bis(benzaldehyde thiosemicarbazones) 27 and 28 with p-chlorophenacyl bromide 29. Compounds 27 and 28 were obtained by condensation of the corresponding bis(aldehydes) 12 and 13 with thiosemicarbazide 26.

GRAPHICAL ABSTRACT

Keywords:

• bis(α-bromoketones)
• alkylation
• cyclization
• condensation
• bis(thiazole)
• thieno[2,3-b]thiophene