N-Binucleophiles. Formation of 2-Oxoimidazolidines

The formation of several cyclic ureas by methods employing phosgene equivalents has been discussed in part in Section 4.3.4. In this Section, additional interesting cyclization examples and methods are described. 

The N-deprotected pseudopeptides 1113 and 1115 were cyclized to the corresponding 2-oxoimidazolidines with triphosgene and triethylamine in dry dichloro-methane at 0 °C [796-798], 

Other interesting similar examples are presented below [796, 799]  

Cydic urea 1125 has been obtained with triphosgene and EtsN in THF at 25 °C [800], 

Triphosgene has proved to be of general utility in dosing anilino heterocydes 1126 to the corresponding quinazolinone ring systems 1127 [801]. 

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