A cyclization of 1,2-bisureido compounds with sodium nitrite.

Nitrosation of bisureido compounds with sodium nitrite in the presence of acid was examined. The treatment of 1, 2-bisureidoethane with sodium nitrite in 6% sulfuric acid, afforded 1-carbamoyl-3-nitroso-2-imidazolidinone in 86% yield. Similarly, the same nitrosation of 1, 2-bisureidopropane gave an isomeric mixture of cyclized N-nitroso compounds in 87% yield. On the other hand, nitrosation of o-phenylenebisurea with sodium nitrite and 25% sulfuric acid, gave only cyclized 1-carbamoyl-2-benzimidazolidinone in 58% yield, and nitroso compound was not obtained. This nitrosative cyclization occurs only in 1, 2-bisureido compounds which have no substituent in the ureido nitrogens. The mechanism of this cyclization was also discussed.