Treating derivatives of m-phenylenediamine having different electron-richness and reactivities with triphosgene in the presence of triethylamine led to aromatic tetraurea macrocycles in high yields. Factors important for efficiently forming these macrocycles include the molar ratio (2:1) between the diamine and triphosgene, reaction temperature (-75 °C), and solvent (CH2Cl2). By controlling the order and rate for adding diamines, tetraurea macrocycles consisting of two different types of monomeric residues have also been obtained in high yields.
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Wu et al. (2012) studied this question.
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