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Topic: replacing an alcohol with an iodine using triphenylphosphine (Ph3P) and imid  (Read 18950 times)

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Offline g-bones

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replacing an alcohol with an iodine using triphenylphosphine (Ph3P) and imid
« on: April 07, 2008, 12:44:16 AM »
anybody know how an alcohol can be replaced with an iodine when using Ph3P, imid, and I2?  anyhelp would be great.   
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Offline Dan

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Re: replacing an alcohol with an iodine using triphenylphosphine (Ph3P) and imid
« Reply #1 on: April 07, 2008, 03:03:58 AM »
It's basically the same as the Appel reaction:

http://www.organic-chemistry.org/namedreactions/appel-reaction.shtm

but you are using I2 instead of CI4, the reactive intermediate is the same: Ph3P+I
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Offline g-bones

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Re: replacing an alcohol with an iodine using triphenylphosphine (Ph3P) and imid
« Reply #2 on: April 07, 2008, 04:34:30 AM »
yeah but in that situation there is no base strong enough, the only anion is I- when triphenylphospine splits the I2.  not strong enough to deprotanate an alcohol like a carbon base.  right?
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Offline Dan

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Re: replacing an alcohol with an iodine using triphenylphosphine (Ph3P) and imid
« Reply #3 on: April 08, 2008, 10:43:31 AM »
Fair point, but Ph3P+I is electrophilic enough to be attacked by alcohols. The HI generated is "mopped up" by the imidazole.
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