Phosphorus pentachloride with ureas

Other reagents that have been used to effect the dehydration of ureas to carbodiimides are alkyl chloroformates (for thioureas) [46], phosgene [47], phosphorus oxychloride [48], and phosphorus pentachloride [38, 49]. Di-chlorocarbodiimides have been shown to be intermediates when COCl2 or PC15 reacts with ureas (Eq. 13). If R1 and R3 are H, then the intermediate... 

Nitration of p-nitroaniline (15b), or reacting picric acid with phosphorus pentachloride, yields trinitrochlorobenzene, which on amination affords 2,4,6-trinitroaniline, the explosive picramide. Phosgenation of /V-ethylaniline (26) gives a substituted urea used as a stabilizer for explosives. Diphenylamine (8) is used as a stabilizer, for nitrocellulose explosives as well as for celluloid, and also as a solid rocket propellant. Ethylaniline 26 is employed in the manufacture of centralite, a stabilizer in smokeless powder. Other uses for 15b, the largest volume nitroaniline, include in the production of dyes, antioxidants and pharmaceuticals. 

We have observed that in the reaction of N-monosubstituted ureas with phosphorus pentachloride attack on nitrogen as well as on oxygen occurs, depending upon the substituents attached to nitrogen... 

A special case involves reaction of benzoyl ureas XXX with phosphorus pentachloride, which most likely occurs via a concerted cyclic elimination process... 

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