A new one-pot synthesis of 5,5-disubstituted hydantoins from diethyl acetamidomalonates and ureas

A new one-pot synthesis of 5,5-disubstituted hydantoins 3 is reported. Diet hyl 2-acetamido-2-alkylmalonates were found to react with substituted ureas in the presence of sodium ethoxide to produce the 5-alkyl-5-carbamoylhydan toins 3 a-e. The reaction involves a ring contraction of intermediate 5-ami nobarbituric acids to the final hydantoin derivatives. The 5-aminobarbituri c acids 2 d-f were prepared from azido derivatives 6 d-f. On treatment with sodium ethoxide, 2 d-f underwent the rearrangement to afford the hydantoin s 3 d-f.