Base-Promoted Formal Arylation of Benzo[<i>d</i>]oxazoles with Acyl Chloride

A base-promoted formal arylation of benzo­[<i>d</i>]­oxazoles with acyl chloride was achieved in moderate to good yields. This reaction was triggered by the <i>N</i>-acylation of oxazole to form an iminium intermediate. Then, the addition of H₂O to the iminium formed the hemiacetal intermediate. After the sequential ring-opening, extrusion of CO, the ring closure, the dehydration delivered the formal arylation product. In comparison with the transition-metal-catalyzed methodology, it represents an alternative arylation method leading to 2-arylbenzooxazole

Rhodium-Catalyzed Direct Annulation of Aldehydes with Alkynes Leading to Indenones: Proceeding through <i>in Situ</i> Directing Group Formation and Removal

The Rh-catalyzed direct annulation of an aldehyde with an alkyne leading to indenone was achieved. The <i>in situ</i> temporal installation of acetylhydrazine enables the annulation of the <i>ortho</i> arene C–H bond with alkynes to form ketone hydrazone. Subsequently, the <i>in situ</i> directing group removal takes place since ketone hydrazone is more susceptible toward hydrolysis than aldehyde hydrazone. Notably, this procedure tolerates a series of functional groups, such as methoxyl, acetylamino, fluoro, trifluoromethyl, methoxycarbonyl, chloro, and bromo groups