42506-03-6

9-Chloro-9-phenylxanthene was used in the preparation of (1S,5S,6R,8S)-6-[(allyloxycarbonyl)oxy]-5-(trifluoroacetamido)-8-[9′-(9′-phenylxanthenyl)oxy]-2-oxabicyclo(3.2.1)octane.

A possible impurity is 9-hydroxy-9-phenylxanthene. If the material contains a lot of the hydroxy product, then boil 10g of it in CHCl3 (50mL) with redistilled acetyl chloride (1mL) until liberation of HCl is complete. Evaporation leaves the chlorophenylxanthene as the hydrochloride which on heating with *benzene loses HCl; and on adding pet ether prisms of chlorophenylxanthene separate and contain 0.5mol of *benzene. The *benzene-free compound is obtained on drying, and it melts to a colourless liquid. [Gomberg & Cone Justus Liebigs Ann Chem 370 142 1909.] The 9-phenylxanthyl group is called “pixyl” and is a good protecting group [Chattopadhyaya & Reese J Chem Soc, Chem Commun 639 1978, Beilstein 17 III/IV 1704.]