Method B: Hydrogenation (PtO,/H,). Hydrogen gas was bubbled into the stirred mixture of 30 mg (0.1 1 mmol) of 24 and 10 mg of PtO,(Adam'catalyst) in 25 mL of ethanol at room temperature. The reaction mixture turned reddish brown from yellow quickly, and the brown color disappeared gradually. After the solution turned colorless, the catalyst was removed by filtration and the filtrate, which turned dark violet gradually, was concentrated in vacuo to ...
