We report herein an effective method for the halogenation of imidazo-fused heterocycles using readily available sodium salts (NaCl/NaBr/NaI) as halogen source and K 2 S 2 O 8 (or) oxone as promoter. A variety of C-3 halogenated imidazo[1,2-a]pyridines and benzo[d]imidazo[2,1-b]thiazoles were obtained in good to excellent yields. The present method of halogenation has been also extended to 2-aminopyridines, 2-aminopyrimidine, indole, and isoquinoline with moderate to excellent yields.
Tetrabutylammonium hydroxide catalysed oxidative amidation and thioamidation of benzylamines with oxygen and elemental sulfur under solvent/metal/base-free conditions have been developed.
Copper-catalyzed
synthesis of disulfenylated imidazo[1,2-a]pyridines
and indoles using elemental sulfur and haloarenes
through one-pot, three component reaction by two C–S–C
bond formations has been developed. The method has a broad substrate
scope with a variety of substituted haloarenes. The conditions were
also applied for the synthesis of benzothieno-imidazo[1,2-a]pyridines in excellent yields (99%) through intramolecular
sulfenocyclization of 2-(2-halophenyl)imidazo[1,2-a]pyridines using sulfur powder.
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