Sciencemadness Discussion Board - Why This Reaction Doesn't Happen ???

Why This Reaction Doesn't Happen ???

(Brain)2NH - 29-7-2013 at 10:34

I know this question is a general one, but the answer will surely help me understand basic things in reactions grasping.

I found in shulgin's book that indole reaction with Oxalyl chloride, yields 2-(1H-indol-3-yl)-2-oxoacetyl chloride.
(attached image)

my question is NOT : the second reaction happens or not ?
I know it doesn't happen.
my question is : why the second reaction doesn't happen ?
cause there's a chlorine there and there are other indoles with intact C-3 carbon.

maybe my question is a booby one, but it's just what sparkled out of my curiosity.

TnX

kristofvagyok - 29-7-2013 at 10:52

From TIHKAL:

Quote:

To a well stirred solution of 10 g indole in 150 mL anhydrous Et2O there was added, dropwise over the course of 30 min, a solution of 11 g oxalyl chloride in 150 mL anhydrous Et2O. Stirring was continued for an additional 15 min during which time there was the separation of indol-3-ylglyoxyl chloride as a yellow crystalline solid. This intermediate was removed by filtration and washed with Et2O. It deteriorates at a significant rate at room temperature, and should be used as soon as possible after preparation.

Two main reasons why the second reaction only happens on negligible scale: Is the indole in excess? No. Is the indol-3-ylglyoxyl chloride soluble in the reaction mixture? No.

Crowfjord - 29-7-2013 at 11:08

In the procedure from TIHKAL, indole is kept in excess of oxallyl chloride by adding a solution of oxallyl chloride to a solution of indole, slowly. Furthermore, the product, indol-3-ylglyoxyl chloride precipitates as it is formed (as far as I can tell from the procedure), so it cannot appreciably react further with more indole.

If the procedure were reversed, adding solution of indole to a solution of oxallyl chloride, the symmetric product you wonder about would probably be the major product. What would that be called, by the way? Bis-indol-3-ylglyoxyl?

Are you sure the bis-indole product doesn't form AT ALL? I wouldn't be surprised if it did in small amounts as a side reaction.

Edit: Dang, Kristoff beat me to it as I was typing... Oh well

[Edited on 29-7-2013 by Crowfjord]

(Brain)2NH - 29-7-2013 at 11:19

Quote: Originally posted by Crowfjord

Are you sure the bis-indole product doesn't form AT ALL?

[Edited on 29-7-2013 by Crowfjord]

maybe it very little traces of it forms.
cause shulgin says the yield after making the corresponding amide is 79%.
so can't be sure whether the first reaction or amidation causes this yield drop.