[Jumpingelephant]

I have some mono tetraphenylporphyrin (Structure:http://link.springer.com/static-content/images/230/art%253A10.1007%252Fs00706-011-0586-3/MediaObjects/706_2011_586_Figa_HTML.gif). I'm currently using 1:1:2 molar ratio TPP:DCC:NHS in chloroform stirred for 2 hours and there is no NHS esters present. I've tried different molar ratios, temps, stirring times etc and there are still no NHS esters present. Any ideas?

[phth]

If one coupling reagent is not working then why not use another? There are many.  Did you make sure your DCC is not urea?

[Jumpingelephant]

Yeah it is definitely DCC. I forgot to mention, stupidly enough, that when running a TLC it shows the TPP activated by the DCC but no presence of NHS ester, just a single NHS spot. So it looks like the first step is working but not the amide formation.

[Babcock_Hall]

Some couplings involving DCC call for catalytic amounts of DMAP.  I have not surveyed the literature on NHS esters, but I have looked into the topic of active esters a little bit.

[Jumpingelephant]

In the literature we have read we haven't seen the use of any catalysts. We were originally using catalytic amounts of NMM, but with no success.

[salteen]

Do you have any base in your mixture, i.e. DIPEA? This is more essential for other coupling reagents but it has helped for me in the past.

I typically run DCC/EDC  couplings in DMF - Not sure if switching solvents would help your case but might be worth a shot.

[discodermolide]

I don't think that the TPP activated by DCC will be visible on TLC, it is not usually stable to silica-gel.