Direct Assembly of Diverse Unsymmetrical Tertiary 9-Fluorenols via Transient Directing Group-Enabled Palladium-Catalyzed Dual C-H Bond Activation of α-Ketoesters.

An expeditious construction of an unsymmetrical tertiary 9-fluorenol skeleton was accomplished starting from readily available α-ketoester and aryl iodide. Inexpensive commercially available substituted aniline was utilized as a potent monodentate transient directing group (TDG) to assist palladium-catalyzed direct ortho-C-H arylation and tandem dual C-H activation of α-ketoesters to form two carbon-carbon bonds. To demonstrate practical applications, the reaction was enlarged to the gram scale, and subsequent one-step derivatization allowed facile access to structurally diversified useful derivatives. A series of control experiments were carried out to shed light on the possible catalytic mechanism.

Monodentate Transient Directing Group Assisted Ruthenium(II)-Catalyzed Direct ortho-C-H Imidation of Benzaldehydes for Diverse Synthesis of Quinazoline and Fused Isoindolinone.

2-Fluoro-5-(trifluoromethyl)aniline was found to be a suitable monodentate transient directing group (MonoTDG) to enable Ru(II)-catalyzed intermolecular direct ortho-C(sp2)-H imidation of benzaldehydes. N-Tosyloxyphthalimide was used as an alternative azide-free amidation reagent to achieve high efficiency and good functional group tolerance. Moreover, the reaction could be enlarged to gram scale, and the amidated product could be readily converted into useful quinazoline and fused isoindolinone scaffolds by one-step derivatization.