Hydrochloric Acid → 9H-xanthene-3,6-diol

Beteiligte Stoffe

Reaktionsschritte

To a suspension of 3,6-dihydroxyxanthone (46 g, 201 mmol.) obtained as in Example 1 in 1.6 L of THF was added over 1 hr 800 ml of borane-tetrahydrofuran complex (1.0M in THF, caution very vigorous raction at beginning). This mixture was stirred overnight under argon at room temperature to give a clear yellow solution. The excess diborane was decomposed by careful addition of water followed by 1N HCl to give a clear yellow solution. The tetrahydrofuran was removed by rotary evaporation and the resulting solid filtered, washed with water and redissolved in 10% NaOH. This solution was filtered, cooled and reprecipitated with slow addition of HCl to give a yellow solid which was filtered, washed with water and dried under vacuum to give 40.14 g (93%, mp 207-208) of 3,6-Dihydroxyxanthane. H1NMR (DMSO): 9.41 (s, 2H); 6.97 (d, 2H, J=8.4 Hz), 6.4 (dd, 2H, J=8.4, 2.4 Hz), 6.39 (d, 2H, J=2.4 Hz), 3,765 (s, 2H).

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