Aza-crown ether
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Through Organic chemistry, Nitrogen and Amine
Synthesis
The synthesis of aza crown ethers are subject to the challenges associated with the preparation of macrocycles. The 18-membered ring in (CH2CH2NH)6 can be synthesized by combining two triamine components. By reaction with tosyl chloride, diethylene triamine is converted to a derivative with two secondary sulfonamides. This compound serves as a building block for macrocyclizations.
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Variants
Many kinds of aza crown ethers exist.
- Variable length linkers
Aza crowns often feature trimethylene ((CH2)3) as well as ethylene ((CH2)2) linkages. One example is cyclam (1,4,8,11-tetraazacyclotetradecane).
- Tertiary amines
In many aza-crown ethers some or all of the amines are tertiary. One example is the tri(tertiary amine) (CH2CH2NCH3)3, known as trimethyltriazacyclononane. Cryptands, three-dimensional aza crowns, feature tertiary amines.
- Mixed ether-amine ligands
Another large class of macrocyclic ligands feature both ether and amines.. One example is the diaza-18-crown-6, [(CH2CH2O)2(CH2CH2NH)]2.
- Lariate crowns
The presence of the amine allows the formation of Lariat crown ethers, which feature sidearms that augment complexation of cation.