Synthesis of (1S*, 2S*, 3S*, 4S*, 5S*, 6S*, 7S*, 8S*)-1,2,7,8-tetrachlorotricyclo[4.2.0.03,8]octane-4,5-dicarboxylic acid. Novel entry into the C 2-bissecocubane system

Photocaging of the known Diels–Alder dimer of 2,3-dichlorocyclopentadienone, compound 1, followed by alkali-induced double ring-cleavage of the resulting caged diketone rac-2 or its dihydrate rac-3, led to the title tetrachloro dicarboxylic acid rac-5, thus affording a novel entry into the inherently chiral tricyclo[4.2.0.03,8]octane (C2-bissecocubane) system. Electrolysis of the disodium salt of rac-5 gave the tetrachloro alkene rac-14, from which other derivatives were obtained by standard methods.