G. Mehta, A. Srikrishna, A. V. Reddy
1981
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Tetrahedron
Abstract
Abstract Fifteen examples of a new, speedy and general approach to linearly fused tricyclopentanoids bearing the tricyclo[6.3.0.0 2,6 ]undecane (triquinane) frame of high contemporary interest is delineated. The key concept in our synthetic sequence to triquinanes is the novel photo-thermal olefin metathesis of cheap, abundantly available Diels-Alder adducts of 1,3 cyclopentadienes and p-benzoquinones. Thus photolysis of endo -tricyclo[6.2.1.0 2,7 ] undeca-4,9-dien-3,6-diones ( 9a – 9j , 13a,b ) furnished pentacyclo [5.4.0.0 2,6 .0 3,10 .0 5,9 ]undecan-8,11-diones ( 10a – 10j , 14a,b ), which on thermal fragmentation of the cyclobutane ring gave cis , syn , cis -tricyclo [6.3.0.0 2,6 ]undeca-4,9-dien-3,11-diones ( 11a – 11j , 15a,b in just three steps and in exceptionally good yields. A few interesting transformations of the readily available parent bis-enone 11a which indicates its wider uses in syntheses, are described. Finally, a smooth thermal isomerisation of cis , syn , cis -bis-enones to cis , anti , cis -bis-enones is reported, which further enhances the scope and versatility of our synthetic theme.