Unsaturated B-homo ketones

B-Homosteroids have also been prepared by acid-catalyzed reaction of diazomethane with a,/5-unsaturated ketones. 3/ -Hydroxycholest-5-en-7-one acetate (57) reacts with diazomethane in the presence of concentrated fluoroboric acid, boron trifluoride etherate or aluminum chloride to give 3yS-hydroxy-B-homo-cholest-5-en-7a-one acetate (67). The 7a-keto group is reported to be chemically less reactive than an 11-keto group. 

3 -Hydroxy-B-homo-choIest-5-en-7a-one Acetate (67) A solution of 3p-hydroxycholest-5-en-7-one acetate (57 0.45 g) in absolute ether (140 ml) is placed in a 500 ml two-necked flask equipped with a mechanical stirrer and a calcium chloride drying tube. An ether solution of diazomethane (15.4 ml 0.42 g = 0.01 mole) is added with stirring at room temperature. Aluminum chloride (50 mg) is then added to the stirred solution. After 5 min an additional 50 mg of aluminum chloride is added. 

After an additional 10 min, a 1 % solution of hydrochloric acid (100 ml) is slowly added to the stirred reaction mixture and the resultant mixture is transferred to a separatory funnel. The ether layer is separated and washed sequentially with water, 5 % sodium bicarbonate solution, water and saturated salt solution. The washed ether solution is dried over anhydrous sodium sulfate, filtered, and evaporated to give an oily residue (0.45 g). Chromatography of the crude product on silica gel (50 g) followed by crystallization of the solid thus obtained (0.18 g) from ethanol gives 3 -hydroxy-B-homo-cholest-5-en-7a-one acetate (67 0.14 g) mp 90-91° [a]o 99° (CHCI3). 

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