A Dieckmann Cyclization Route to Piperazine-2,5-diones

Piperazine-2,5-diones are formed by Dieckmann cyclization (NaH, THF) of substructures of the type CH2-N­(R)­C­(O)­CH2N­(R′)­CO2Ph in which the terminal methylene (CH2) that is adjacent to nitrogen closes onto the carbonyl group of the phenyl carbamate unit at the other end of the chain. R and R′ are alkyl groups, and the terminal methylene is activated by a ketone carbonyl, a nitrile, an ester, or a phosphoryl group. The starting materials are assembled by standard acylation and oxidation processes, starting from a β-(alkylamino)­alcohol, an (alkylamino)­acetonitrile, an (alkylamino) ester, or an (alkylamino)­methyl phosphonate.