Iodine-catalyzed synthesis of benzoxazoles using catechols, ammonium acetate, and alkenes/alkynes/ketones via C–C and C–O bond cleavage

Abstract

A metal-free one-pot multi-component method for the efficient synthesis of 2-aryl benzoxazoles via coupling of catechols, ammonium acetate and alkenes/alkynes/ketones using an I2–DMSO catalyst system is illustrated.

Iodine and DMSO as Surrogate of Hazardous Metal and Non‐Metal Reagents in Organic Synthesis

“…[479,480] Aboonajmi and group developed a more eco-friendly approach to benzoxazole synthesis using 10 mol% of iodine and DMSO as the solvent (Scheme 50 (h)). [481] They used NH 4 OAc as the nitrogen source and alkenes, acetylene, and ketones as carbon sources to react with catechol and produced various benzoxazole derivatives. The proposed mechanistic approach involves the I 2 -DMSO catalyst system, which initiates the conversion of catechol (A) into mono-quinone molecule (B).…”

“…For the synthesis using benzaldehyde and catechol, either Fe(III)‐salen complex or NaIO 4 with NH 4 OAc as a nitrogen source is required (Scheme 50 (e) and (f)) [479,480] . Aboonajmi and group developed a more eco‐friendly approach to benzoxazole synthesis using 10 mol% of iodine and DMSO as the solvent (Scheme 50 (h)) [481] . They used NH 4 OAc as the nitrogen source and alkenes, acetylene, and ketones as carbon sources to react with catechol and produced various benzoxazole derivatives.…”

I2/DMSO-mediated oxidative C–C and C–heteroatom bond formation: a sustainable approach to chemical synthesis

“…Panahi, Sharghi, and colleagues 75 proposed a method to produce benzoxazoles 55 without the use of metals. This involves combining ammonium acetate 54 with catechols 53 and alkenes/alkynes/ketones.…”

One-pot, three-component, iron-catalyzed synthesis of benzimidazolesviadomino C–N bond formation

“…On the other hand, there is a high demand for efficient and clean synthesis of benzimidazole derivatives from other sources. Continuing our program on the synthesis of benzoxazoles, 4,5,31,32 we would like to present here a novel and efficient protocol for the synthesis of benzimidazole derivatives. In this work, MCR of benzo-1,2-quinones, aryl aldehydes and ammonium acetate in the presence of catalytic amount of an Fe(III)-porphyrin catalyst at room temperature resulted in a benzimidazole core.…”