77787-05-4Relevant articles and documents
Synthesis of some bicyclooct-5-en-2-ones and bicyclooctan-2-ones. Rearrangement accompanying oxidative decarboxylation with lead tetraacetate
Yates, Peter,Langford, Gordon E.
, p. 344 - 355 (2007/10/02)
1-Methoxy-2-methyl-1,4-cyclohexadiene (3), 2-methoxy-1-methyl-1,3-cyclohexadiene (2), and 2-methoxy-1,5,5-trimethyl-1,3-cyclohexadiene (14) on heating with maleic anhydride give 1-methoxy-endo-7-methylbicyclooct-5-ene-syn-2,3-dicarboxylic acid anhydride (7) and its 6-methoxy-1-methyl (16a) and 6-methoxy-1,8,8-trimethyl (16b) analogues, respectively.On hydrolysis 16a and 16b give the corresponding keto dicarboxylic acids, 18a and 18b, via keto anhydrides 17a and 17b.Treatment of 18b with lead tetraacetate gives 1,8,8-trimethylbicyclooct-5-en-2-one (19) together with products in which rearrangement to a bicyclooctane system has occured.Treatment of 17b with bis(triphenylphosphino)nickel dicarbonyl gives only 19; similar treatment of 17a gives 1-methylbicyclooct-5-en-2-one (1).Reaction of bicyclooctane-2,3-dione (27) with methyllithium gives 3-hydroxy-3-methylbicyclooctan-2-one (28), its dimer 31, and a diol 30.Treatment of 5-exo-acetoxy-1,5-endo-dimethyl-6-oxobicyclooctane-anti-2,3-dicarboxylic acid (37) with lead tetraacetate gives 3-endo-acetoxy-1,3-exo-dimethylbicyclooct-5-en-2-one (33) as a minor product; the major product is derived by rearrangement to a bicyclooctane system.It is proposed that this rearrangement, like that of 18b, involves oxidative decarboxylation of a single carboxylic acid group to give a carbonium ion that undergoes rearrangement via a 1,2-acyl migration.
