DDQ-mediated oxidation of sp3 C-H bond for the direct synthesis of vicinal tricarbonyl compounds

A facile and direct synthetic method was developed for the construction of vicinal tricarbonyl compounds (VTCs) in moderate to excellent yields (46-92%), by treating the readily available 1,3-dicarbonyl compounds with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) in the presence of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). The reaction pathway involves the DDQ-mediated oxidative activation of sp3 C-H bond and subsequent coupling to TEMPO to form the key intermediate TEMPO-substrate adduct, which can be further converted to VTC products promoted by DDQ.