The Naked Scientists

The Naked Scientists Forum

Author Topic: Wittig reaction - unaffected functional groups  (Read 3808 times)

Offline adianadiadi

  • Jr. Member
  • **
  • Posts: 16
    • View Profile
    • AdiChemistry: An Online Resource of Chemistry Study Material
Wittig reaction - unaffected functional groups
« on: 30/09/2013 15:48:10 »
I would like to know what are the functional groups that are not affected by wittig reaction conditions?


 

Offline chiralSPO

  • Global Moderator
  • Neilep Level Member
  • *****
  • Posts: 1879
  • Thanked: 145 times
    • View Profile
Re: Wittig reaction - unaffected functional groups
« Reply #1 on: 30/09/2013 19:22:39 »
There are many functional groups not affected, including carboxylic acids (which are only deprotonated under the wittig conditions), esters, amides, amidines, ureas etc.

Really it is easier to ask which groups DO react: aldehydes and sterically unencumbered ketones will undergo a wittig condensation. Any compound that has an acidic proton (pKa <20) is likely to be deprotonated under these conditions. Similarly alkyl halides (Cl, Br, I, OTf, OMs, OTs) can potentially undergo E2 eleminitation reactions to produce alkenes.
 

Offline adianadiadi

  • Jr. Member
  • **
  • Posts: 16
    • View Profile
    • AdiChemistry: An Online Resource of Chemistry Study Material
Re: Wittig reaction - unaffected functional groups
« Reply #2 on: 02/10/2013 16:36:36 »
Thank you. I would like to know why not the carbonyl group of esters could also react? Any explanation?
 

Offline chiralSPO

  • Global Moderator
  • Neilep Level Member
  • *****
  • Posts: 1879
  • Thanked: 145 times
    • View Profile
Re: Wittig reaction - unaffected functional groups
« Reply #3 on: 02/10/2013 20:10:25 »
The carbonyl in esters, carboxylic acids and amides are less electrophilic because the electron density on the oxygen or nitrogen is donated into the carbonyl pi system.

Esters are not electrophilic enough to react with phosphorus-based Witting- or HWE-type olefination reagents, however the more reactive metal-based reagents like Tebbe and Petasis can react with esters too.
 

Offline adianadiadi

  • Jr. Member
  • **
  • Posts: 16
    • View Profile
    • AdiChemistry: An Online Resource of Chemistry Study Material
Re: Wittig reaction - unaffected functional groups
« Reply #4 on: 07/10/2013 04:14:36 »
Thank you @chiralSPO
 

The Naked Scientists Forum

Re: Wittig reaction - unaffected functional groups
« Reply #4 on: 07/10/2013 04:14:36 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums