Oxygen diene geometry

The same mixture of H and I was obtained starting with either of the geometrically isomeric radical precursors E or F. A possible explanation is based on the assumption of a common radical conformer G, stabilized in the geometry shown by electron delocalization involving the radicaloid p-orbital, the p-peroxy oxygen and Jt of the diene unit. The structure of the compounds H and I were determined by H NMR spectra and the conversion of H to diol J, a known intermediate for the synthesis of prostaglandins. 

Seven-membered ring trani-alkenes have been accessed diastereoselectively from dienes and aldehydes by the silver-catalysed transfer of silylene (Scheme 13). The trans geometry of the double bond has been assigned from cleavage of the silicon-oxygen bond (path (a)). The high strain of these cyclic trawi-alkenes can... 

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