Reduction of cyanoazatricycloheptane (I) with diisobutylaluminum hydride produced aldehyde (II), which was treated with KCN and ammonia yielding aminonitrile (III). Cyclization of (III) with sulfur monochloride in DMF gave the 3-chloro-1,2,5-thiadiazole (IV). Displacement of the halogen atom of (IV) with sodium hydrogen sulfide, followed by alkylation with propyl bromide afforded the propyl thioether (V), which was oxidized to sulfone (VI) using oxone(R). The arylpropynol intermediate (IX) was prepared by coupling of 1-bromo-3,5-difluorobenzene (VII) with propargyl alcohol (VIII) in the presence of PdCl2(PPh3)2 and CuI. Reaction of sulfone (VI) with arylpropynol (IX) in the presence of NaH in THF provided the target ether (X). Finally, treatment of (X) with oxalic acid in acetone furnished the corresponding oxalate salt.

Reduction of cyanoazatricycloheptane (I) with diisobutylaluminum hydride produced aldehyde (II), which was treated with KCN and ammonia yielding aminonitrile (III). Cyclization of (III) with sulfur monochloride in DMF gave the 3-chloro-1,2,5-thiadiazole (IV). Displacement of the halogen atom of (IV) with sodium hydrogen sulfide, followed by alkylation with propyl bromide afforded the propyl thioether (V), which was oxidized to sulfone (VI) using oxone(R). The arylpropynol intermediate (IX) was prepared by coupling of 1-bromo-3,5-difluorobenzene (VII) with propargyl alcohol (VIII) in the presence of PdCl2(PPh3)2 and CuI. Reaction of sulfone (VI) with arylpropynol (IX) in the presence of NaH in THF provided the target ether (X). Finally, treatment of (X) with oxalic acid in acetone furnished the corresponding oxalate salt.