trans-Cycloalkenes. Part 12. trans,trans- and cis,trans-Cyclonona-1,5-diene
Possible synthetic routes to trans,trans-cyclonona-1,5-diene from the cis,cis-isomer have been investigated using the β-hydroxyphosphine oxide olefin inversion procedure. A stepwise approach via the epoxy-trans-cyclononene (10) failed. However consecutive double elimination involving the bis-β-hydroxyphosphine oxides (11) and (12) gave cis- and trans-1,2-divinylcyclopentane which are believed to have been obtained by rapid Cope rearrangement of first formed ‘parallel’ and ‘crossed’trans,trans-cyclonona-1,5-diene (1A) and (1B) respectively.