Chloroform → 2-chloroformyl-5-oxo-5H-dibenzo[a,d]cycloheptene

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Reaction Steps

A solution of 2.50 g. of 2-carboxy-5-oxo-5H-dibenzo[a,d]cycloheptene in 50 ml. of chloroform, 10 ml. of thionyl chloride and 0.3 ml. of dimethylformamide is stirred for 8 hours, then evaporated to dryness and the residue recrystallized from acetonitrile to yield 2-chloroformyl-5-oxo-5H-dibenzo[a,d]cycloheptene. This is dissolved in 50 ml. of chloroform and added to a 3-fold excess of ethereal diazomethane at 0°C. After 12 hours the solution is evaporated to dryness and the residue recrystallized from acetonitrile to yield 2-diazoacetyl-5-oxo-5H-dibenzo[a,d]cycloheptene. A solution of 1.37 g. of the latter compound in 50 ml. of tetrahydrofuran is added to 10 ml. of 0.1 N sulfuric acid containing 0.5 g. of copper powder. The mixture is refluxed for 3 hours and then cooled, filtered and poured into water. The solution is extracted with ethyl acetate and the extract washed, dried and evaporated to yield 2-hydroxyacetyl-5-oxo-5H-dibenzo[ a,d]cycloheptene which is recrystallized from chloroform/hexane. A solution of 0.05 g. of cupric acetate monohydrate in 5 ml. of acetic acid is heated to 100°C and 3.0 g. of granular zinc is added. The mixture is shaken for 3 minutes and the acetic acid is then decanted. The residual zinc-copper couple is washed three times with 5 ml. portions of acetic acid, then three times with 5 ml. portions of ether. It is then refluxed for four hours under nitrogen in 20 ml. of ether containing 2.5 ml. of methylene iodide, 1.32 g. of 2-hydroxyacetyl-5-oxo-5H-dibenzo[a,d]cycloheptene is added, and reflux is continued for a further four hours. The mixture is cooled and diluted with 50 ml. of benzene. The liquid phase is decanted and washed with water and aqueous sodium bisulfate, then dried and evaporated. The residue is chromatographed on 50 gm. of silica gel, eluting with ethyl acetate/hexane, to yield 2-(5-oxo-5H-dibenzo[a,d]-cyclohepten-2-yl)prop-1-en-3-ol.

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