4,9,14,19‐Tetrafunctionalized Pagodanes de novo Synthesis – Functional Group Manipulations

Various 4,9,14,19‐tetrafunctionalized pagodanes are prepared by a de novo route commencing from appropriately substituted isodrin analogues ( 3, 4 ). With the 14,19‐dimethoxypagodane‐4,9‐dicarboxylic esters 30/31 , isolated after 16 one‐pot operations (ca. 40 functional changes) in ca. 6.5% overall yield (ca. 84% per operation, ca. 93% per functional change), the scope for further functional group manipulations on the pagodane sphere is explored (e.g. diketone dicarboxylic ester 35 , dimethoxy diketone 37 , tetraketone 41 ). In two face‐to‐face dibenzo substrates ( 17, 49 ), clean photoequilibration with the corresponding syn‐o,o' ‐dibenzo isomers ( 19, 50 ) (75: 25 and 80: 20, resp.) is observed upon direct excitation (λ=254 nm).