Synthesis of C-meso and/or C-racemic isomers of tetraaza macrocyclic copper(II) and nickel(II) complexes bearing one or two N-CH2OCH3 pendant arms

Jeong, Gyeong Rok; Kang, Shin‐Geol; Jeong, Jong Hwa

doi:10.1016/j.ica.2011.09.036

Cited by 4 publications

(2 citation statements)

References 23 publications

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“…Coupling of segment 5 with the known compound 4 in the presence of HATU and DIEA yielded compound 13 in 92% yield . Reduction of the azide moiety and deprotection of the Cbz group simultaneously over palladium on activated carbon (10%) under hydrogen yielded the corresponding diamine compound, which was cyclized by formaldehyde to provide hexahydropyridine 14 in 87% yield over two steps . Removal of the TBS group with HF in pyridine afforded the corresponding alcohol, which upon hydrolysis using HCl in dioxane (1 N) gave the originally proposed hetiamacin A (Scheme ).…”

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confidence: 99%

Total Synthesis of Originally Proposed and Revised Structure of Hetiamacin A

Liu

Wang

et al. 2018

Org. Lett.

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confidence: 99%

Total Synthesis of Originally Proposed and Revised Structure of Hetiamacin A

Liu

Wang

et al. 2018

Org. Lett.

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“…No other evidence of this modification of 2 was seen in other characterization techniques, and this appears to be a known phenomenon that can result from copper tetraazamacrocycle complexes usually modifying their own ligands to form the N(macrocycle)-CH 2 OCH 3 pendant arm [ 55 , 61 , 62 , 63 ]. According to reference (Jeong et al) [ 61 ] and reference (Alves et al) [ 55 ], when aminal (N-CH 2 -N) derivatives of tetraazamacrocycles are reacted with MeOH in the presence of M 2+ cations, the N-CH 2 OCH 3 pendant arm can be formed. However, they were unsuccessful at intentionally isolating the ligand, as it appears to be easily hydrolyzed back to the amine.…”

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confidence: 99%

A Bridge too Far? Comparison of Transition Metal Complexes of Dibenzyltetraazamacrocycles with and without Ethylene Cross-Bridges: X-ray Crystal Structures, Kinetic Stability, and Electronic Properties

et al. 2023

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Tetraazamacrocycles, cyclic molecules with four nitrogen atoms, have long been known to produce highly stable transition metal complexes. Cross-bridging such molecules with two-carbon chains has been shown to enhance the stability of these complexes even further. This provides enough stability to use the resulting compounds in applications as diverse and demanding as aqueous, green oxidation catalysis all the way to drug molecules injected into humans. Although the stability of these compounds is believed to result from the increased rigidity and topological complexity imparted by the cross-bridge, there is insufficient experimental data to exclude other causes. In this study, standard organic and inorganic synthetic methods were used to produce unbridged dibenzyl tetraazamacrocycle complexes of Co, Ni, Cu, and Zn that are analogues of known cross-bridged tetraazamacrocycles and their transition metal complexes to allow direct comparison of molecules that are identical except for the cross-bridge. The syntheses of the known tetraazamacrocycles and the new transition metal complexes were successful with high yields and purity. Initial chemical characterization of the complexes was conducted by UV-Visible spectroscopy, while cyclic voltammetry showed more marked differences in electronic properties from bridged versions. Direct comparison studies of the unbridged and bridged compounds’ kinetic stabilities, as demonstrated by decomposition using high acid concentration and elevated temperature, showed that the cyclen-based complex stability did not benefit from cross-bridging. This is likely due to poor complementarity with the Cu2+ ion while cyclam-based complexes benefited greatly. We conclude that ligand–metal complementarity must be maintained in order for the topological and rigidity constraints imparted by the cross-bridge to contribute significantly to complex robustness.

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