反应详情

A. From 2,7-Dichloroxanthene-9-carboxylic Acid: To a suspension of 0.75 g of LiAlH4 in 90 mL of anhydrous ether was added dropwise a solution of 3.0 g of 2,7-dichloroxanthene-9-carboxylic acid in 45 mL of freshly distilled THF over a period of 25 minutes. The mixture was stirred at room temperature until the color had changed from grey to light brown (ca. 6hr). The excess LiAlH4 was decomposed by the slow addition of 10 mL of methanol and 2 mL of water while stirring. The suspended precipitate was filtered, rinsed with ether (2×30 mL) and discarded. The combined filtrate was washed with water (2×40 mL), dried over MgSO4, and evaporated under reduced pressure to give 1.53 g (53.6%) of the alcohol as a white solid. Recrystallization from Skelly B--EtOAc (4:1) gave 1.21 g (42.36%) of the 2,7-dichloro-9-xanthenemethanol as a white fluffy solid, m.p. 134.5°-136° C.; IR (KBr): 3250 (b, OH) cm-1 ; 1H NMR (CDCl3): δ 1.65 (b, 1H, OH), 3.75 (d, 2H, CH2O), 4.01 (t, 1H, CH), 6.94-7.40 (m, 6H, aryl). Anal. Calcd for C14H10O2Cl2 : C, 59.81; H, 3.59. Found: C, 60.73; H, 3.91. B. From 9-Xanthenemethanol: To a suspension of 3.0 g of 9-xanthenemethanol and 4.2 g of N-chlorosuccinimide in 25 mL of freshly distilled THF and 12.5 mL of water was added dropwise 2.0 mL of conc. HCl over a period of 5 minutes. The mixture was stirred at room temperature for 6 hours and poured into 200 mL of water with stirring. The precipitated solid was filtered, rinsed with water (2×30 mL), and dried in air to afford 3.95 g (100%) of the crude alcohol. Recrystallization from Skelly B--EtOAc (4:1) gave 1.35 g (34%) of 2,7-dichloro-9-xanthenemethanol as a fluffy solid, m.p. 134.5°-136° C., identified by the mixture melting point, IR and NMR spectral comparison with an authentic sample obtained by the reduction of 2,7-dichloroxanthene-9-carboxylic acid.

1. customRecrystallization from Skelly B
2. customEtOAc (4:1) gave 1.21 g (42.36%) of the 2,7-dichloro-9-xanthenemethanol as a white fluffy solid, m.p. 134.5°-136° C.
3. stirringwith stirring
4. filtrationThe precipitated solid was filtered
5. washrinsed with water (2×30 mL)
6. customdried in air