An efficient synthesis of N,N′-linked oligoureas

Abstract

This paper reports an efficient synthesis of N-alkyl- N,N′-linked oligoureas [NRCONHCH 2CH 2] 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CH 2CH 2NHSO 2Ar (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CH 2CH 2NHR″). A tetraurea was prepared in 10 steps and 58% overall yield by this method.