Perchloric Acid Catalyzed Homogeneous and Heterogeneous Addition of β-Dicarbonyl Compounds to Alcohols and Alkenes and Investigation of the Mechanism

The direct addition of various β-dicarbonyl compounds to a series of secondary alcohols and alkenes has been achieved using 1 mol % perchloric acid (HClO4) as the catalyst. The HClO4-catalyzed reactions could be conveniently conducted in commercial solvent and gave moderate to excellent yields. Moreover, the silica gel-supported HClO4 could also catalyze the heterogeneous addition for a series of substrates with similar or even higher yields in comparison with the homogeneous ones. The supported catalyst could be readily recovered and reused for four runs. Furthermore, the mechanism of the HClO4-catalyzed addition of the β-diketone to alcohol was investigated, and an SN1 mechanism was proved unambiguously for the first time through a series of experiments. The discrimination of catalytic abilities among different Brønsted acids was also rationalized by DFT calculations.