Dess-Martin periodinane (DMP), a highly versatile hypervalent
iodine(V) reagent, was found to efficiently mediate the intramolecular
cyclization of phenolic azomethines/Schiff bases at ambient
temperature leading to the rapid and expeditious synthesis of substituted
benzoxazoles and benzothiazoles. Furthermore, a solution-phase strategy
has been developed by treating the reaction mixtures sequentially
with Amberlyst A-26 thiosulfate resin and diisopropylaminomethyl
resin (PS-DIEA), which remove excess reagent and byproducts, to
give pure products.
Dess-Martin periodinane - intramolecular cyclization - azomethines - benzoxazoles
- benzothiazoles - solution-phase strategy