Carbodiimides hydration

At higher acidities the S-nitrosation reaction of thiourea leads to the formation of urea64 (equation 28) via, it is believed, the intermediate formation of the S-nitroso species. The reaction can also be brought about by nitrosamines or alkyl nitrites as the carriers of NO+. Reaction is thought to involve nucleophilic attack of the intermediate by water or the elimination of HSNO giving a carbodiimide, which is then hydrated. 

Hydration of carbodiimide (HN=C=NH) is described under Mines below. 

A solution of the Step 7 product (0.16 mmol) and 1-hydroxybenzotriazole hydrate (0.16 mmol) in CH2C12 was cooled to 0°C, then stirred 30 minutes, and treated sequentially with pyrrolidine (0.16 mmol), 3-ethyl-3 -(dimethylamino)propyl-carbodiimide hydrochloride (0.16 mmol), and 60 pi triethylamine. Stirring was continued for additional 30 minutes at 0°C and 2 days at ambient temperature. The mixture was then partitioned between 1.5 ml water and 20 ml EtOAc and combined organic extracts washed with 1.5 ml brine, dried with Na2S04, and concentrated. 

Overall, the hexameric resorcin[4]arene capsule showed very interesting selective properties for the condensation reaction between carboxylic acids and amines mediated by a cationic carbodiimide-based condensing agent similarly to what was observed in the previous case for the alkyne hydration reaction, the capsule prefers the encapsulation of smaller and more compact substrates that react faster than longer ones. 

Anhydrous HCl will add exothermically to form the dichloro compound, while mineral acids will catalyze hydration of the carbodiimide. Perhaps... 

Abbreviations CDMT = 2-chloro-4,6-dimethoxy-l,3,5-triazine EDCI = l-ethyl-3-(3-dimethyla-minopropyl)carbodiimide BOP = benzotriazol-l-yloxy-tris-(dimethylamino)phosphonium hexa-fluorophosphate DIPEA = diisopropylethylamine DEPC = diethylphosphoryl cyanide CBM IT = l,l-carbonylbis(3-methylimidazolium triflate HOBt = 1-hydroxybenzotriazole hydrate HBPyU = 0-(benzotriazole-l-yl)-iV,Af,A,Af-bis(tetramethylene)uronium hexafluorophosphate. 

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