Synthesis of 3-(6-R-Benzothiazol-2-yl)-4-methyl-1,2,5-oxadiazoles

Abstract

The nitrosation of N-aryl-3-oxobutanethioamides afforded 1-(6-R-benzothiasol-2-yl)-1-hydroxyimino-2-propanones that at oximation with hydroxylamine were converted into 1-(6-R-benzothiazol-2-yl)-1,2-dihydroxyiminopropanes. The latter were dehydrated by heating with succinic anhydride at 140°C yielding therewith 3-(6-Rbenzothiazol-2-yl)-4-methyl-1,2,5-oxadiazoles.

Mild Synthesis of Substituted 1,2,5-Oxadiazoles Using 1,1′-Carbonyldiimidazole as a Dehydrating Agent

“…To this end, a typical reaction entails refluxing the precursor in a high-boiling solvent (100–150 °C) in the presence of a strong base, such as NaOH or KOH, followed by direct precipitation of the product or extractive workup. Various activating reagents, including Ac 2 O, SOCl 2 , succinic anhydride, ,, and others, , have been reported to facilitate this cyclization, but temperatures greater than 100 °C are typically required.…”