Aza-crown ether

The structure of [Co(III)(CH₂CH₂NH)₆]³⁺.^[1] Color code: blue = N, gray = C, black = C, white = H.

In organic chemistry, an aza-crown ether is an aza analogue of a crown ether (cyclic polyether).^[2]^[3] That is, it has a nitrogen atom (amine linkage, −NH− or >N−) in place of each oxygen atom (ether linkage, −O−) around the ring. While the parent crown ethers have the formulae (CH₂CH₂O)_n, the parent aza-crown ethers have the formulae (CH₂CH₂NH)_n, where n = 3, 4, 5, 6. Well-studied aza crowns include triazacyclononane (n = 3), cyclen (n = 4),^[4] and hexaaza-18-crown-6 (n = 6).^[5]

Selected aza-crowns and their complexes
1,4,7-Trimethyl-1,4,7-triazacyclononane, a tridentate ligand used in coordination chemistry.
Cyclam is a tetraaza crown ether with alternating (CH₂)₂ and (CH₂)₃ linkers between amine centers.
Plerixafor, a derivative of cyclam, is used to treat lymphoma and multiple myeloma.^[6]
2.2.2-Cryptand is an aza-crown of the mixed ether-amine variety.

^ Morooka, M.; Ohba, S.; Toriumi, K. (1992). "Electron-density distribution in crystals of 1,4,7,10,13,16-hexaazacyclooctadecanecobalt(III) trichloride, meso-[Co(hexaen)]Cl3 at 106 K". Acta Crystallographica Section B: Structural Science. 48 (4): 459–463. doi:10.1107/S0108768192002714.
^ Bencini, Andrea; Bianchi, Antonio; Garcia-España, Enrique; Micheloni, Mauro; Ramirez, José Antonio (1999). "Proton coordination by polyamine compounds in aqueous solution". Coordination Chemistry Reviews. 188: 97–156. doi:10.1016/S0010-8545(98)00243-4.
^ Reichenbach-Klinke, Roland; König, Burkhard (2002). "Metal complexes of azacrown ethers in molecular recognition and catalysis". Journal of the Chemical Society, Dalton Transactions (2): 121–130. doi:10.1039/b106367g.
^ Reed, David P.; Weisman, Gary R. (2002). "1,4,7,10-Tetraazacyclododecane". Org. Synth. 78: 73. doi:10.15227/orgsyn.078.0073.
^ Cite error: The named reference atkins was invoked but never defined (see the help page).
^ "Plerixafor". Drugs in R&D. 8 (2): 113–119. 2007. doi:10.2165/00126839-200708020-00006. PMID 17324009.

[1] Morooka, M.; Ohba, S.; Toriumi, K. (1992). "Electron-density distribution in crystals of 1,4,7,10,13,16-hexaazacyclooctadecanecobalt(III) trichloride, meso-[Co(hexaen)]Cl3 at 106 K". Acta Crystallographica Section B: Structural Science. 48 (4): 459–463. doi:10.1107/S0108768192002714.

[2] Bencini, Andrea; Bianchi, Antonio; Garcia-España, Enrique; Micheloni, Mauro; Ramirez, José Antonio (1999). "Proton coordination by polyamine compounds in aqueous solution". Coordination Chemistry Reviews. 188: 97–156. doi:10.1016/S0010-8545(98)00243-4.

[3] Reichenbach-Klinke, Roland; König, Burkhard (2002). "Metal complexes of azacrown ethers in molecular recognition and catalysis". Journal of the Chemical Society, Dalton Transactions (2): 121–130. doi:10.1039/b106367g.

[4] Reed, David P.; Weisman, Gary R. (2002). "1,4,7,10-Tetraazacyclododecane". Org. Synth. 78: 73. doi:10.15227/orgsyn.078.0073.

[atkins-5] Cite error: The named reference atkins was invoked but never defined (see the help page).

[DrugsRD-6] "Plerixafor". Drugs in R&D. 8 (2): 113–119. 2007. doi:10.2165/00126839-200708020-00006. PMID 17324009.

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