A
50-ml., round-bottomed flask, equipped with a
Teflon®-covered magnetic stirring bar and a
reflux condenser connected to a
gas-inlet tube, is charged with
970 mg. (2.51 mmoles) of cholest-4-en-3β-ol (Note
1) and
30 ml. of o-xylene (Note
2). The mixture is stirred to effect solution before
1.67 g. (0.0125 mole) of N,N-dimethylacetamide dimethyl acetal (Note
3) is added. The flask is flushed with
argon, then heated (Note
4) at reflux under a positive pressure of
argon with vigorous stirring for 65 hours. After cooling, the volatile materials are removed at reduced pressure (Note
5), and the yellow, oily residue (1.2 g.) is chromatographed on
60 g. of silica gel with
diethyl ether (Note
6). Elution of the column with
200 ml. of ether gives a mixture of cholestadienes which is discarded; further elution with
500 ml. of ether affords
740 mg. of
N,N-dimethyl-5β-cholest-3-ene-5-acetamide as a clear, colorless oil, which on trituration with
acetone gives
740 mg. (
65%) of the amide as white plates, m.p.
128–129.5°.