FORMATION OF TETRAACETAL OXA-CAGES AND CONVEX OXA-CAGES ON OZONOLYSIS OF BICYCLO[2.2.2]OCTENES

Tetraacetal oxa-cage compounds 5a and 5b and convex era-cage compounds 7a and 8a are synthesized in a short sequence. Ozonolysis of endo adducts 2a and 2b in dichloromethane at -78 degrees C followed by reduction with dimethylsulfide gave tetraacetal era-cages 5a and 5b in 35 % yields respectively. Ozonolysis of 2a in dichloromethane at -78 degrees C followed by treatment with triethylamine gave the convex era-cage 7a in 34% yield. These results support an acid-base proton transfer between the final ozonides and the base. The reasons that these era-cage compounds formed in low yields are discussed. The synthesis of tetraacetal oxa-cage 14, possessing aromatic substitutents directly on the skeleton of the era-cage, is accomplished.