Visible‐Light Induced Oxidative Annulation of Enamides to 2,4,5‐Trisubstituted Oxazole Skeletons

Abstract

A novel approach to various trisubstituted oxazoles (28 examples, up to 88% yield) has been developed via 9Hthioxanthen-9-one (TX) mediated oxidative annulation of Nacetyl enamide under visible light irradiation in the presence of BF 3 • Et 2 O (2.0 equiv) and 40 mol% of PhNO 2 . This metal-free procedure features high atom and step economy, green and mild conditions and broad substrate scope.

Recent Advancements in Strategies for the Synthesis of Imidazoles, Thiazoles, Oxazoles, and Benzimidazoles

“…in 2023 (Scheme 75). [97] This metal‐free process has great atom and step economies, moderate and environmentally friendly conditions, and a wide substrate scope. Various EDG and EWG‐substituted phenyl moieties of enamide at the ortho , meta , and para positions have resulted in the generation of the oxazole scaffolds in moderate to excellent yield.…”

Crafting mono- and novel bis-methylated pyrroloquinoxaline derivatives from a shared precursor and its application in the total synthesis of marinoquinoline A

“…Traditional synthetic methods to access pyrroloquinoxalines substituted at the 4-position are toxic and dangerous. 12 Among the prevailing methodologies, the most prominent routes entail the reduction of 1-(2-nitrophenyl)pyrroles to their corresponding amino derivatives. 13 Treatment of the amino group with acid chlorides to generate the corresponding acetamides, followed by intramolecular cyclisation under Bischler–Napieralski conditions, thus furnishing the core of the 4-substituted pyrrolo[1,2- a ]quinoxaline structure.…”