Diaminotoluene reaction with, phosgene

Toluene Diisocyanate. Toluene diisocyanate is the basic raw material for production of flexible polyurethane foams. It is produced by the reaction sequence shown below, in which toluene is dinitrated, the dinitrotoluene is hydrogenated to yield 2,4-diaminotoluene, and this diamine in turn is treated with phosgene to yield toluene 2,4-diisocyanate. 

The reactions of the dihydrochloride salts of 2,4- and 2,6-diaminotoluene with phosgene in toluene or 1,2-dichlorobenzene solutions have been examined at 25-90 C [1923]. With the 2,4-isomer, acylation occurs initially at the 2-position, followed by a slower acylation at the 4-position direct acylation of both NHj groups occurs at equal rates in the... 

Cyclizations can occur when two amino groups are adjacent on a benzene ring. For example, reaction of phosgene with 2,3-diaminotoluene in chlorobenzene gave a precipitate containing a five-membered ring, considered to be a cyclic urea [1154] ... 

One of the most important uses of phosgene is the production of isocyanate for polyurethane. For example, toluene diisocyanate is produced by the reaction of diaminotoluene with phosgene [reaction (16)]. 

---