epoxidation: substitution vs. conjugation

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RoseBrilliante
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Bit of a dilemma: trying to figure out which alkene m-CPBA / H2O2 in base will react with. I've attached a picture of the starting molecule; there's an internal, more substituted alkene in the ring and there's a terminal one outside of the ring.
I would've thought that since the internal alkene is conjugated with an electron-withdrawing group (the carbonyl group) that that would make the alkene more electron-poor, so the hydroperoxide anion would attack there in a nucleophilic fashion, but the problem is that this alkene is more substituted than the terminal one, which causes the alkene to become more nucleophilic: apparently the electrophilic oxygen on m-CPBA would be attacked by the internal one instead and then H2O2 would attack the terminal alkene.

Does this mean that the conjugation has less effect than the fact that it is more substituted? If so, does it mean that the H2O2 mechanism is concerted like the m-CPBA one? Bit of a long shot but if anyone replies, thanks
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alow
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(Original post by RoseBrilliante)
Bit of a dilemma: trying to figure out which alkene m-CPBA / H2O2 in base will react with. I've attached a picture of the starting molecule; there's an internal, more substituted alkene in the ring and there's a terminal one outside of the ring.
I would've thought that since the internal alkene is conjugated with an electron-withdrawing group (the carbonyl group) that that would make the alkene more electron-poor, so the hydroperoxide anion would attack there in a nucleophilic fashion, but the problem is that this alkene is more substituted than the terminal one, which causes the alkene to become more nucleophilic: apparently the electrophilic oxygen on m-CPBA would be attacked by the internal one instead and then H2O2 would attack the terminal alkene.

Does this mean that the conjugation has less effect than the fact that it is more substituted? If so, does it mean that the H2O2 mechanism is concerted like the m-CPBA one? Bit of a long shot but if anyone replies, thanks
The epoxidation of an electron deficient double bond by hydrogen peroxide is called the Juliá-Colonna epoxidation (https://www.wikiwand.com/en/Juli%C3%...na_epoxidation). It is not concerted like epoxidation via MCPBA, it's more akin to an E1cb.

I would be very cautious using MCPBA in a molecule with a carbonyl, as it's fairly likely Baeyer Villiger oxidation would occur (hydrogen peroxide can also cause this but you would need different reaction conditions).
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RoseBrilliante
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(Original post by alow)
The epoxidation of an electron deficient double bond by hydrogen peroxide is called the Juliá-Colonna epoxidation (https://www.wikiwand.com/en/Juli%C3%...na_epoxidation). It is not concerted like epoxidation via MCPBA, it's more akin to an E1cb.

I would be very cautious using MCPBA in a molecule with a carbonyl, as it's fairly likely Baeyer Villiger oxidation would occur (hydrogen peroxide can also cause this but you would need different reaction conditions).
Thank you for the link, didn't think the H2O2 mechanism was concerted. So am I right in thinking that the hydroperoxide anion would attack the alkene that's conjugated with the carbonyl group, even though it's more substituted than the terminal one?
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alow
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(Original post by RoseBrilliante)
Thank you for the link, didn't think the H2O2 mechanism was concerted. So am I right in thinking that the hydroperoxide anion would attack the alkene that's conjugated with the carbonyl group, even though it's more substituted than the terminal one?
I would think so, yes.
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RoseBrilliante
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(Original post by alow)
I would think so, yes.
Thank you!
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