7.7- Dichlorobicyclo 3 2 0 hept-2-en-6-one

B. Tropohne. In a 1-1., three-necked, round-bottomed flask equipped with a mechanical stirrer, addition funnel, and reflux condenser are placed 500 ml. of glacial acetic acid and then, cautiously, 100 g. of sodium hydroxide pellets. After the pellets have dissolved, 100 g. of 7,7-dichlorobicyclo[3.2.0]hept-2-en-6-one is added and the solution is maintained at reflux under nitrogen for 8 hours. Concentrated hydrochloric acid is then added until the mixture is about pH 1 approximately 125 ml. of acid is required. After the addition of 1 1. of benzene, the mixture is filtered and the solid sodium chloride is washed with three 100-ml. portions of benzene. The two phases of the filtrate are separated and the aqueous phase is transferred to a 1-1. continuous extractor (Note 8) which is stirred magnetically. The combined benzene phase is transferred to a 2-1. pot connected to the extractor and the aqueous phase is extracted for 13 hours. Following distillation of the benzene, the remaining orange liquid is distilled under reduced pressure... 

Fractions were analyzed by vapor-phase chromatography (column 0.3 X 120 cm., 20% SE-52 on Chromosorb P 60/80, 130°, helium flow rate of 60 ml./min.). Retention times of 1.9 minutes for dicyclopentadiene and 4.6 minutes for the 7,7 dichlorobicyclo[3.2.0]hept-2-en-6-one were found. 

Bicyclo[3.2.0]hept-2-en-6-one. A solution of freshly distilled tributyltin hydride (31 g, 0.108 mol) (1) in cyclohexane (30 ml) is placed in a three-necked flask equipped with a reflux condenser, a nitrogen inlet tube and a dropping funnel. The flask is flushed with nitrogen. The solution is refluxed while a solution of 7,7-dichlorobicyclo[3.2.0]hept-2-en-6-one (5.83 g, 0.054 mol) in cyclohexane containing a,a -azobisisobutyronitrile (AIBN) (0.1 g, 0.6 mmol) is gradually added. After completion of the addition the mixture is distilled to give 4.38 g (75%) of bicyclo[3.2.0]hept-2-en-6-one (b.p. 62 °C/20 mmHg), no5... 

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