GreenD - 27-3-2013 at 10:44
Hey,
I'm trying to find a good general procedure for regenerating carbodiimides from the urea product.
This guy has a method
http://www.cmld.ku.edu/Publications/2004Zhang2.pdf "Dehydration of Urea 3 To Form Monomer Carbodiimide 4. Using the same procedure as shown in ref
21, to a suspension of urea 3 (1.15 g, 3.47 mmol) in triethylamine (2.4
mL, 17.3 mmol) was added phenylsulfonyl chloride (1.02 mL
6.9 mmol) at rt. After the addition was completed, the esulting suspension was stirred and heated to 70 °C for 1.5 h. The reaction was quenched with
ice-water and partitioned between water and ether. The organic portion was separated, washed with water and brine, dried (MgSO4), and concentrated
under reduced pressure. The residue was purified by column chromatograph (40% EtOAc in hexanes) to obtain 793 mg of required carbodiimide 4 (73%):"
(ref 21 is impossible to find)
And there is this patent which I cannot get to:
http://ip.com/patfam/en/43367720
I'm sure there must be other methods, phenylsulfonyl chloride just seems like a very specific choice to do such a reaction.
Any help would be appreciated.
GreenD - 27-3-2013 at 10:59
Whoa:
"Procedure for regeneration of PS-cyclohexylcarbodiimide (PSCC). The polymer bound cyclohexylurea (PSCU; 1 g of 1.25 mmol/g) recovered after
N-acylation was suspended in DCM (20 mL) in a three-neck round-bottomed flask (100 mL) equipped with a silicon rubber septum and a reverse
filter funnel under exclusion of moisture and air.26 Phosphorus oxychloride (POCl3) (0.38 g, 2.5 mmol) was added slowly over a period of 10
min to the above suspension. The mixture was vortexed gently for 4–6 h and the supernatant was removed by reverse filtration and replaced by 10%
aqueous NaOH (5 mL) and fresh dichloromethane (20 mL). The suspension was shaken further for 1 h and the aqueous supernatant was removed. The polymer
was washed with THF (2× 25 mL) to remove excess water and dried under vacuum to furnish PSCC."
http://www.sciencedirect.com/science/article/pii/S0960894X05...
Citation 26:
Fujibayashi, R. (Sumikin Kakoh Co. Ltd.), Jpn. Pat. Appl. No. 95-37375, February 24, 1995.
Have no idea how to access.
[Edited on 27-3-2013 by GreenD]
sonogashira - 28-3-2013 at 05:52
I have used the P2O5 method successfully. I don't know why both of the files have been renamed, but they are both pdf files, if you want to open them
manually.
Attachment: phpry3fhb (76kB)
This file has been downloaded 1266 times
Attachment: phpLlw1fi (170kB)
This file has been downloaded 1453 times
[Edited on 28-3-2013 by sonogashira]