Ziklen

Cyclen can be synthesized by combining two separate components in a nucleophilic substitution reaction . ^[1] In this case, the terminal amino groups in diethylenetriamine (1) are activated as amine anionic nucleophiles in the reaction with tosyl chloride in pyridine with the formation of a protected N-tosyl group with the subsequent replacement of protons in the reaction with sodium ethoxide . The alcohol end groups of diethanolamine (2) are activated as electrophiles by replacing with Tosyl leaving groups . The components thus obtained are combined in dimethylformamide with a strong dilution of the components. However, if the concentration of the components is not sufficiently low, a simple polymerization reaction is possible with the formation of long chains and without cyclization. In the last synthetic reaction, after the formation of cyclic compound (6), the tosyl groups are removed in the presence of sulfuric acid to form cyclen (7).

Since the above reaction requires a high dilution of the components, which leads to a low yield, an alternative synthesis has been proposed. It begins with triethylentetraamine and dithiooxamide to form an intermediate amidine and a subsequent reduction reaction in the presence of diisobutyl aluminum hydride. ^[2]

Due to its complexing properties, cyclin is used as a contrast agent in magnetic resonance imaging .

• Cycles

• Suchý, M .; Hudson, RHE Synthetic Strategies Toward N- Functionalized Cyclens (Eng.) // Eur. J. Org. Chem. : journal. - 2008. - Vol. 2008 , no. 29 . - P. 4847—4865 . - DOI : 10.1002 / ejoc.200800636 .

• Metal complexes of macrocyclic ligands. 1. New tetra-azamacrocyclic ligands.