Planarisierung von tetrakoordiniertem Kohlenstoffatom. Synthese des überbrückten all‐cis‐[5.5.5.5]Fenestrans 13‐Oxapentacyclo[5.5.2.11.7.04,15.010,15] pentadecan‐14‐on

Planarisation of Tetracoordinate Carbon Atom, Synthesis of the Brigded all‐cis‐[5.5.5.5]Fenestrane 13‐Oxapentacyclo[5.5.2.11,7.04,15.010,15]pentadecan‐14‐one The synthesis of the ketolactone 23 from (Z,Z)‐1,5‐cyclooctadiene is reported. Transannular carben insertion, achieved via photolysis of the deprotonated (2,4,6‐trisisopropylphenylsulfonyl)hydrazone of 23 gives the bridged all‐cis‐[5.5.5.5]fenestrane 3.