Total synthesis of furanether B. An application of a [3 + 4] annulation strategy

Article abstract of DOI:10.1021/jo00120a030

Furanether B has been synthesized by a route starting from the known dichloro ketone 6. Crucial to the success of the synthesis was the preparation of cyclobutene 5 and oxidative cleavage of this substrate to provide the cis-1,4-keto aldehyde 3. This dicarbonyl dielectrophile subsequently underwent a TMSOTf catalyzed [3 + 4] annulation with the bis(trimethylsilyl) enol ether 4 to afford the tricyclic ether 2. Conversion of 2 into butenolide 19, followed by DIBALH reduction, completed the synthesis.