Total Syntheses of Ring Intact Limonoids:1,2-Dihydroazadirone, Azadirone, Azadiradione and Epoxyazadiradione

Intact limonoids are an important class of limonoids with diverse biological activities. Herein, we report a concise and convergent route for the synthesis of four intact limonoids from readily available sclareolide in 12 to 15 steps. Key transformations include: 1) a selective oxidation of sclareolide at the C3 position via a C-H oxidation; 2) an intermolecular Mukaiyama-type aldol reaction for the convergent formation of the C12-C13 bond with an all-carbon quaternary center at C13; 3) a Pd-catalyzed Heck reaction for construction of the central six-membered C-ring in a stereocontrolled manner.