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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: darkdevil on September 22, 2014, 05:21:20 AM

Title: Vilesmeier - Haack Formylation
Post by: darkdevil on September 22, 2014, 05:21:20 AM

Dear,

I am doing the formylation of this compounds using Vilesmeier Reagent (DMF + POCl3)
However, when doing NMR analysis I found the that aldehyde group was attached on the nitrogen atom instead of the aromatic ring.
(https://www.chemicalforums.com/proxy.php?request=http%3A%2F%2Foi61.tinypic.com%2F33kxem0.jpg&hash=da3d99c5231f1d765e3eeea771b6c867bb8f8ab9)

I saw wikipedia demonstrated a similar reaction with Indole, and the reaction occurs at the ring. The only difference is that I used DMF as solvent while they used toluene. Does the solvent effect really that matter?
(https://www.chemicalforums.com/proxy.php?request=http%3A%2F%2Fupload.wikimedia.org%2Fwikipedia%2Fcommons%2F5%2F5f%2FIndole_Vilsmeyer-Haack_Formylation.png&hash=79aa52b9144c6cf79730720a1a764e6d924f74e4)

Thanks!

Title: Re: Vilesmeier - Haack Formylation
Post by: discodermolide on September 22, 2014, 06:18:46 AM

The solvent won't make much difference, usually you need traces of DMF. It's not surprising that it N-formylated, where did you expect to react?

Title: Re: Vilesmeier - Haack Formylation
Post by: darkdevil on September 22, 2014, 07:19:09 AM

I expect it to react at the aromatic ring

Title: Re: Vilesmeier - Haack Formylation
Post by: discodermolide on September 22, 2014, 09:05:25 AM

Perhaps you should try protecting the NH groups. Even then I am not convinced that it formylate the aromatic ring(s).