Synthesis of Tetraacetal Pentaoxa-Cages and Convex Oxa-Cages by Ozonolysis of 7-Oxabicyclo[2.2.1]heptenes

Abstract

Tetraacetal pentaoxa-cage compounds 4a and 4b and convex oxa-cage compounds 6, 7 and 8 are synthesized from alkylfurans in three steps. Ozonolysis of the endo adducts 2a and 2b in dichloromethane at -78°C followed by reduction with dimethyl sulfide gave the tetraacetal pentaoxa-cages 4a and 4b in 85-90% yields, respectively. Ozonolysis of 2a and 2b in dichloromethane at -78°C followed by treatment with triethylamine gave the convex oxa-cages 6, 7 and 8 in 85-90% yields, respectively. The synthesis of the tetraacetal pentaoxa-cage 12, possessing aromatic substituents directly on the skeleton of the oxa-cages, has also been accomplished.