[Sach]

Hi guys, I did direct arylation to get the following molecule (dimethyl 4,4'-(3-(((benzyloxy)carbonyl)amino)thiophene-2,5-diyl)dibenzoate), see attachment for the molecule. I took an H-nmr spectrum that you can find in the word document (total spectrum and zoomed in). I am relatively new to H-nmr although i did study it to be able to interpret it.
To start the interpratation, from my understanding of the H-nmr, there should be 8 types of hydrogens but on the spectrum I can only see 6 type of hydrogens. i am not sure if I missed anything so far.
But is there any chance this spectrum could belong to the molecule I posted in the attachment?
Thank you in advance

[rolnor]

I do not beleive its the wanted product, have you compared it with the NMR och the Cbz-amino thiophene? The aromatic area looks like this startingmaterial.

[Sach]

Yes I did and it doesn't really look like the starting material. The tlc also confirmed that there was no Cbz-protected thiophene after the direct arylation.

[rolnor]

OK, I think the benzylic CH2-protons should be downfield compared to the methylester-protons? You have almost seven prototons at 3,9ppm and I think it would be strange if the benzylic and methylester-protons came at this same shift. The aromatic protons could be OK though. The peaks you have at 1-1,5ppm is probably impurity.

[rolnor]

I checked now and the methylester-protons should come lower than i expected so I think your compound is OK.

[Sach]

But shouldn't I have 8 types of hydrogens on the spectrum because my molecule has 8 different types of hydrogens? Tomorrow, I have to tell my professor which peak belongs to which hydrogen but I still couldn't figure it out.

[rolnor]

Sorry Sach, what is missing is the benzyloxycarbonyl group, both the benzyl-CH2 and from the phenyl-ring.
The benzyl-CH2 should be att 5ppm and not at 4ppm if I am not mistaking. I have no explanation for this.

[Sach]

No problem, I still can't thank you enough.

[Sach]

According to the H-nmr, is there any chance that this is my molecule with protecting group removed? So thiophene with both benzene rings and NH.

[rolnor]

Yes, I have been thinking that too, do you have a mass-spectrometer in the lab?

[Sach]

My professor was also thinking that this could be the molecule with the protecting group removed and that would be actually good news. No we don't have a mass spectrometer but I can take a C-nmr on another campus.

[wildfyr]

Why don't you do a TLC stain or assay to see if you have a free amine? Such as this trick (https://www.thermofisher.com/order/catalog/product/28997)

Perhaps you could even see if it will go back and forth between aqueous and organic phases using dilute acid and base washes

[Sach]

I will see if it's possible with a compound we have available because otherwise we probably won't buy it.
But thnx a lot.

[Sach]

I got the following result from C-nmr. The number of carbon environment more or less checks out but I can't see an ester in this spectrum (chemical shift 150-200). You can find the spectrum in the attachment. This is not my unprotected molecule like I thought unless I missed something. Is there someone who can confirm this?
Thnx in advance

[hypervalent_iodine]

Personally, I would rerun that. The signal to noise ratio isn't great, so you're quite possibly not seeing peaks because they're lost to the background.