Transformation of a spirobarbituric acid via aminobarbituric acid-hydantoin rearrangement

摘要

A successful application of the aminobarbituric acid-hydantoin rearrangement to produce a bicyclic carbamoylhydantoin from an intermediate spirobarbituric acid is reported. 7a-Phenylcarbamoyltetrahydro-1H-pyrrolo[1,2-c]imidazole-1,3(2H)-dione (8) was obtained in a one-pot multistep reaction of 1-acetyl-2,2-bis(ethoxycarbonyl)pyrrolidine (5) and phenylurea in the presence of sodium ethoxide. Under less severe conditions, 5 and phenylurea were reacted to afford 1-acetyl-7-phenyl-triaza[4,5]decane-6,8,10-trione (6). The structural elucidation of the bicyclic hydantoin 8 and the spirobarbituric acid 6 was based on relevant nmr signals in accordance with those of reference compounds, i.e. monocyclic hydantoins 4a,b and acetamidobarbituric acids 2a-c. The latter compounds were newly prepared from diethyl acetamidomalonates 1 and phenylurea.