Synthesis of benzoxazoles via an iron-catalyzed domino C–N/C–O cross-coupling reaction

Abstract

The synthesis of benzoxazoles via an iron-catalyzed cascade C–N and C–O coupling is described.

Cascade Transformation of the Ansamycin Benzoquinone Core into Benzoxazole Influencing Anticancer Activity and Selectivity

“…Therefore, many different approaches involving semisynthetic, mutasynthetic, and genetic manipulations have been applied to benzenoid ansamycins in order to reduce the quinone, improve useful biological potency, and decrease toxicity. ,− Modifications of the GDM core via the fusion of additional rings, imidazole, morpholine, benzo­[ g ]­quinoxaline, benzoxazine, oxazolidine, and tetrahydrodiazepine at C(17)–C(18), were rarely accompanied by reduction of the quinone core. Moreover, reported synthetic strategies did not enable further tailoring of the structure of the attached substituent to the core toward interactions with the target (heat shock protein Hsp90). , Modern synthetic strategies affording benzoxazole systems are based mainly on bifunctional reactants. − Unfortunately, these approaches allow the transformation of bifunctional reactants via intermolecular reactions utilizing metal catalysts, which is in contradiction to green chemistry rules. , To the best of our knowledge, benzoxazoles have never been obtained via an intramolecular and metal-free strategy directly from amino-benzoquinones as a starting material, whereas approaches with metal catalysts are very widespread. − …”

“… 35 , 36 To the best of our knowledge, benzoxazoles have never been obtained via an intramolecular and metal-free strategy directly from amino-benzoquinones as a starting material, whereas approaches with metal catalysts are very widespread. 37 − 41 …”