New Ring Cleavage Reactions and Recyclizations Starting from 1,2,3-Thiadiazoles

Abstract

4-Monosubstituted 1,2,3-thiadiazoles are known to decompose in the presence of base to afford the alkynethiolates. When a suitable nucleophilic function is present, a cyclization can occur. Starting from 4-(o-hydroxyphenyl)-1,2,3-thiadiazole 1, benzofurans 4 were obtained after reaction with an alkylating agent.^[1] In an ¹H-NMR spectroscopic study, we observed that both the phenolate 2 and the alkynethiolate 3 are intermediates in this reaction. Dihydroxyphenyl or hydroxynaphthyl substituted 1,2,3-thiadiazole derivatives were also converted to the corresponding hydroxybenzofuran and naphthothiophene systems 5 and 6, respectively.

Keywords::

• 1,2,3-thiadiazoles
• alkynes
• ring cleavage
• cyclization
• benzofurans