Synthesis of 6/6/6-tricyclic ether system via Achmatowicz and intramolecular oxa-michael reactions

Synthesis of 6/6/6-tricyclic ethers possessing 1,3-diaxial methyl groups was examined via Achmatowicz reaction and intramolecular oxa-Michael reaction. A key precursor was prepared via coupling of an aldehyde with a furyllithium derivative followed by radical deoxygenation of the resulting secondary alcohol. The intramolecular oxa-Michael reaction proceeded in a stereoselective manner to afford cis-fused product as a single isomer.