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en***ter image description here The goal is to dihydroxylate the exo alkene, and then convert to a ketone.

Any suggestions would be apprecitated to either chemoselectively convert the terminal alkene, or directly convert the terminal alkene to a ketone.

Thank you!

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  • $\begingroup$ Maybe complete gradual oxidation of methyl having allylic hydrogens would be better idea. $\endgroup$
    – Mithoron
    Apr 1, 2020 at 16:32

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The Lemieux-Johnson oxidation (details here) using catalytic $\ce{OsO4}$ or $\ce{RuO4}$ turned over with $\ce{NaIO4}$ will do the transformation you want in one step. These conditions should be selective for the exo double bond.

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  • $\begingroup$ Thank you! I was hitting a roadblock. $\endgroup$
    – Ellie
    Apr 2, 2020 at 13:37
  • $\begingroup$ @Ellie If you are happy with this, please accept the answer $\endgroup$
    – Waylander
    Apr 2, 2020 at 14:02
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To confirm, you want to make (R)-4-acetyl-1-methylcyclohex-1-ene? Do you have to start from (S)-limonene?

If not, consider the Diels-Alder reaction of isoprene and methyl vinyl ketone (e.g. https://doi.org/10.1039/B701333G , though this is not an enantioselective synthesis I imagine you can add chiral auxiliaries somewhere to increase that selectivity)

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  • $\begingroup$ Thank you. I was considering that as well. $\endgroup$
    – Ellie
    Apr 2, 2020 at 13:36

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