PhI(OAc)2-mediated intramolecular oxidative aryl-aldehyde Csp(2)-Csp(2) bond formation: metal-free synthesis of acridone derivatives.

A metal-free protocol for direct aryl-aldehyde Csp(2)-Csp(2) bond formation via a PhI(OAc)2-mediated intramolecular cross-dehydrogenative coupling (CDC) of various 2-(N-arylamino)aldehydes was developed. The novel methodology requires no need of preactivation of the aldehyde group, is applicable to a large variety of functionalized substrates, and most of all provides a convenient approach to the construction of biologically important acridone derivatives.