Stereoselective Preparation of Hexahydro dibenzopyranones and intermediates therefor

Stereoselective Preparation of Hexahydro dibenzopyranones and intermediates therefor 

A solution of 77 mg. of (-)-cis-l-hydroxy-3-(l,l-dimethylheptyl)-6,6-dimethyl-6,6a,7,8,10,10a-hexahydro-9H-dibenzo[b,d]pyran-9-one in 5 mL. of dicblorometbane containing 77 mg. of aluminum chloride was stirred at 25° C. for four hours. The reaction mixture then was diluted with 20 g. of ice, and the resulting aqueous mixture was extracted with diethyl ether. The ethereal extracts were combined, washed with 2N hydrochloric acid and with ten percent aqueous sodium bicarbonate solution, and then washed with water, dried, and the solvent was removed by evaporation under reduced pressure to provide 75 mg. of the product as an oil. The oil so formed was chromatographed over a thick layer silica gel coated plate. Elution of the principle band with a twenty percent solution of ethyl acetate in benzene, and evaporation of the solvent therefrom, afforded 54 mg. of (-)-trans-l-hydroxy-3-(l,l-dimethylheptyl)-6,6-dimethyl-6,6a,7,8,10,10a-hexahydro-9H-dibenzo[b,d]pyran-9-one. [a]20D - 53.8° (c = 1.0, CHCB). 

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Archer, R.A. Day, W.A. Stereoselective Preparation of Hexahydro dibenzopyranones and Intermediates Therefor 1978 US 4,102,902 Archer, R.A. Lemberger, L. Hexahydro-dibenzo[b,d]pyran-9-ones as Antiasthmatic Drugs 1978 US 4,087,546... 

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