Simple and Efficient Aromatic C-H Oxazolination.

Aromatic oxazolines are versatile in organic synthesis as directing groups, ligands, and protected carboxylic acids. Developing efficient approaches to oxazoline from an aromatic C-H bond is more desirable compared to the established protocols from carboxylic acid and its equivalents. Herein, a simple and efficient aromatic C-H oxazolination with broad substrate scope is described. By employing this transformation as an enabling step, diversity-oriented synthesis of functionalized arenes and target-oriented synthesis of four drugs were accomplished. Mechanistic experiments suggest that this aromatic oxazolination is an electrophilic aromatic substitution. It is anticipated that this transformation will find applications in aromatic C-H functionalization with oxazoline either as a removable directing group or as a masked carboxylic acid.