Nucleophilic intramolecular cyclization reactions of alkynechalcogenolates

2-(ortho-Hydroxyphenyl)-alkynethiolates and -selenolates, obtained through base catalyzed ring cleavage of 4-(ortho-hydroxy phenyl)-1,2,3-thiadiazoles and -1,2,3-selenadiazoles, smoothly transform into 2-benzofuranthiolates and -selenolates. These reactive intermediates can be alkylated in high yield. This reaction sequence could be applied to the synthesis of electron rich thiacrown ethers. The 2-(ortho-aminophenyl)-alkynethiolate analogously forms 2-methylsulfanylindole. (C) 2000 Elsevier Science Ltd. All rights reserved.