Preparation of substituted imidazolidinones and hydantoins by ring-expansion of aziridinones

Reaction of 1,3-di-tety-butylaziridinone and other di-tert-alkylaziridinones with cyanamides produces an imidazolidinone (3 or 6) bearing the tert-alkyl substituents at positions 1 and 5 only, by selective cleavage of the acyl-nitrogen bond. Treatment of the product from the unsubstituted cyanamide (3) with HNO2 furnishes the corresponding hydantoin (5), whereas treatment with alkyl halides and base affords another imidazolidinone (7).