An Efficient Synthesis of 2,3,5,6-Tetramethylidene-7-oxanorbornane

Palladium‐catalyzed double carbomethoxylation of the Diels‐Alder adduct of furan and maleic anhydride yielded the methyl all‐exo‐7‐oxanorbornane‐2,3,5,6‐tetracarboxylate (7) which was transformed in three steps into 2,3,5,6‐tetramethylidene‐7‐oxanorbornane (1), a useful synthon. Six isomeric methyl 7‐oxanor‐bornane‐2,3,5,6‐tetracarboxylates (7–12) have been isolated and their 1H‐ and 13C‐NMR. data are compared.