[polymer man]

Hi ,

I am level four student and in my project I have prepared Diketopyrrolopyrrole:

http://image.made-in-china.com/4f0j00BeHaJiNnwWoM/3-6-Dithiophene-Diketopyrrolopyrrole.jpg

But I can not explain the preparation mechanism in my report. So, can you help me.

The prepartion method is:

A mixture of Na (0.490 g, 21.3 mmol) and a catalytic
amount of FeCl3 was dissolved in tert-amyl alcohol (10 mL)
by heating at 90 C for 2 h. After cooling to 50 C, thiophene-
2-carbonitrile (0.990 mL, 10.6 mmol) was added and
then the mixture was again heated at 90 C. A solution of
dibutyl succinate (1.00 mL, 4.26 mmol) in tert-amyl alcohol
(5 mL) was added dropwise over 2 h and then the mixture
was maintained at 90 C for 20 h. After cooling to 50 C,
glacial AcOH was added and then the mixture was heated
under reflux for 10 min before being filtered. The residue
was washed several times with hot MeOH and water, and
then the solid was dried under vacuum to yield 1 (0.8 g,
63%). This compound was used directly in the next step
without purification.


thank you in advance

[Rose-white]

Hi, I'm not sure if it's good advice, but I would start with that:

[discodermolide]

Sodium tertiary amylate is the base, I think. Sodium salt of thiophene as the reactive species?

[fledarmus]

I don't know, you're starting with an awfully strong base not to have the first productive step be pulling a proton someplace...

My guess is that you form the sodium amylate to be your base as discodermolide said, but the thiophene really doesn't have any acidic protons. Dibutyl succinate does - I would expect that the reason you add it dropwise at 90C is that you pull one alpha proton, couple it to the carbon of a thiophene nitrile group followed by an intramolecular cyclization, then pull the other proton and couple it to the carbon of a second thiophene nitrile group. The succinate is added slowly so each drop sees a large excess of both base and thiophene.

[polymer man]

Hi,

Rose-white

ermolide

fledarmus

many thanks for your help, I understand what happen now.

But what is the reason for using FeCl3?

Thank you again for your help