Stereoselective Synthesis of Bicyclo[4.2.1]nonane Skeletons by Ring‐Closing Metathesis: A New Versatile Methodology for the Efficient Assembly of Functionalized Cyclooctanoids.

Abstract

The title methology combines a stereoselective anionic domino α,γ-difunctionalization of β-ketoesters with ring-closing metathesis resulting in a formal three-carbon ring expansion. Direct retro-Dieckmann cleavage of bridged ketone (IIa) to liberate the corresponding fused eight-membered is carried out producing a 1:1 mixture of the diastereomers. Product (XI) is successfully transformed to the corresponding monotosylate precursor for a stereoselective Grob-type fragmentation. On reaction with KHMDS in THF, aldehyde (XII) is produced diastereoselectively in 45% yield. -(MICHAUT, A.; MIRANDA-GARCIA, S.; MENENDEZ, J. C.; RODRIGUEZ*, J.; Org. Lett. 6 (2004) 18, 3075-3078; React. Synth. Org., Cent. St. Jerome, Univ. Paul Cezanne, F-13397 Marseille, Fr.; Eng.) -Steudel 50-048