Application of the Bucherer hydantoin synthesis to diacetyl mono-oxime. The mechanism of the Bucherer reaction, and the constitution of the hypothetical ? dimethylbishydantoin ? of Bucherer and lieb

Abstract

The major product obtained when the Bucherer conditions for hydantoin synthesis were applied to diacetyl mono-oxime was (3aRS,6aSR)-6-amino-1,3,3a,6a-tetrahydro-1-hydroxy-3a,6a-dimethylpyrrolo[3,4-d]imidazole-2,4-dione (3). Two minor products (7) and (9) are related to (3) but a third, the imidazole 1-oxide (10), is not. Compound (10) was obtained from diacetyl mono-oxime and ammonium carbonate in the absence of cyanide. It is proposed that 4,4-disubstituted 5-imino-oxazolidin-2-ones (18), postulated by Bucherer and Steiner to be intermediates in hydantoin syntheses, rearrange to hydantoins by a base catalysed E1cB mechanism. It is further proposed that (3) is the hypothetical ‘dimethylbishydantoin ’(35) reported by Bucherer and Lieb in 1934.