An efficient synthesis of N,N'-linked oligoureas

Article abstract of DOI:10.1016/S0040-4039(98)01396-3

This paper reports an efficient synthesis of N-alkyl-N,N'-linked oligourcas [-NR-CO-NH-CH₂CH₂](n), which involves the repetition of three steps: (1) main-chain extension by ring-opening of N-(2- nitrobenzenesulfonyl)-2-imidazolidone (1) by a secondary amine RR'NH to afford sulfonamide RR'N-CO-NH-CH₂CH₂-NH-SO₂Ar (2) side-chain attachment by N-alkylation of the sulfonamide with alkyl halide R'X, and (3) removal of the sulfonyl group to give a new secondary amine RR'N-CO NH-CH₂CH₂-NHR'). A tetraurea was prepared in 10 steps and 58% overall yield by this method.