Lactones with Endocyclic Allylic Alkenes

The authors reasoned that the boat transition states were the only energetically accessible ones. For lactones bearing a CT stereocenter, the transition state placing the Cl substituent in a pseudo-equatorial position would be preferred to avoid allyUc strain present in the alternative transition state. The method led to concise syntheses of the monoterpenoids chrysanthemic acid and isodihydronepatalac-tone. 

Also in 1982, Knight and Cameron reported Ireland-Claisen rearrangements of lactones possessing both endocyclic and exocydic allyhc alkenes [88]. They also found low dsjtrans selectivity in the rearrangement of 14- and 15-membered ring lactones. 

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