MECHANISTIC STUDY OF BASE-PROMOTED REARRANGEMENT OF 1,5-DIBROMOPENTACYCLO[5.3.0.0(2,5).0(3,9).0(4,8)]DECANE-6,10-DIONE TO 10-OXA-9-OXOPENTACYCLO[5.3.0.0(2,4).0(3,6).0(5,8)]DECANE-3-CARBOXYLIC ACID

The conversion of 1,5-dibromopentacyclo[5.3.0.0(2,5).0(3,9).0(4,8)]decane-6,10-dione (1) to 10-oxa-9-oxopentacyclo [5.3.0.0(2,4).0(3,6).0(5,8)]decane-3-carboxylic acid (6) on treatment with 5% aqueous potassium hydroxide was shown to proceed through 1, exo-7-dibromo-9-oxotetracyclo[4.3.0.0(2,5).0(3,8)]nonane-endo-4-carboxylic acid (2). Treatment of 1 with the base in heavy water gave rise to 2-d-6 deuterated at the 2-position, but 2 gave the protium analog 6 after the same treatment. These results are discussed in relation to reactions of similar compounds which have been previously described in the literature.