Base-Promoted Domino Reaction of 5‑Substituted 2‑Nitrosophenols with Bromomethyl Aryl Ketones: A Transition-Metal-Free Approach to 2‑Aroylbenzoxazoles
journal contributionposted on 06.11.2015, 00:00 by Nayyef Aljaar, Chandi C. Malakar, Jürgen Conrad, Uwe Beifuss
The reaction of 5-substituted 2-nitrosophenols with bromomethyl aryl ketones and related compounds employing K2CO3 as a base in refluxing THF and DMF at 80 °C, respectively, delivers 2-aroylbenzoxazoles in a single step with yields up to 85%. The new method involves an intermolecular nucleophilic substitution followed by intramolecular 1,2-addition and elimination. It allows an efficient and practical access to 2-aroylbenzoxazoles under transition-metal-free conditions.