Diethyl Ether → Triphenylphosphine Oxide

Participants

Reaction Steps

2.15 gms. of triphenylphosphine and 2.85 gms. of tetrabromomethane were added to a solution of 1.65 gms. of 19-hydroxy cholesterylacetate [prepared according to the method of J. Am. Chem. Soc. 86(1964), 1528] in 70 mls. of dry ether and 10 mls. of dry m-xylene. A white precipitate of triphenylphosphine oxide was formed. Then the mixture was refluxed for 20 hours, the progress of the reaction being examined with the aid of thin-layer chromatography (toluene/ethyl acetate 3:1; silica gel H). After completion of the reaction 100 mls. of n-hexane and 0.5 mls. of methanol were added and approx. 15 minutes later the mixture was filtered and the filtrate evaporated. The residue was taken up in 10 mls. of ether and thereafter 15 mls. of n-hexane were added. Then this hexane/ether mixture was brought on to a column filled with 40 gms. of deactivated Al2O3 and subsequently was eluated with an ether/n-hexane mixture (2:3). The composition of the column fractions was examined with the aid of thin-layer chromatography. The fractions, in which 19-bromocholesterylacetate was present, (Rf = 0.7) were collected and evaporated at a film evaporator. Upon crystallization of the residue from ether/methanol, 1.45 gms. of the product were obtained, having a melting point of 91°-92° C. The structure was confirmed by means of NMR- and mass-spectrometry.

Provenance & Evidence