- Enhanced reactivity of twisted amides inside a molecular cage
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When an amide group is distorted from its planar conformation, the conjugation between the nitrogen lone pair and the π* orbital of the carbonyl is disrupted and the reactivity towards nucleophiles is enhanced. Although there are several reports on the synthesis of activated twisted amides, amide activation through mechanical twisting is much less common. Here, we report twisted amides that are stabilized through their inclusion in a self-assembled coordination cage. When secondary aromatic amides are included in a Td-symmetric cage, the cis-twisted conformation is favoured over the trans-planar one—as evidenced by single-crystal X-ray diffraction analysis—revealing that the amide can twist by up to 34°. As a consequence of this distortion, the hydrolysis of amides is significantly accelerated upon inclusion. [Figure not available: see fulltext.]
- Takezawa, Hiroki,Shitozawa, Kosuke,Fujita, Makoto
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p. 574 - 578
(2020/05/05)
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- Studies on some Mixed-ligand Complexes og Cobalt(II), Nickel(II), Copper(II) and Zinc(II) with Pyridine-2-carboxylic Acid and Thiophene-2-carboxylic Acid
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The formation of ternary metal(II)/thiophene-2-carboxylic acid/pyridine-2-carboxylic acid complexes with CoII, NiII, CuII and ZnII, has been studied potentiometrically at 25 and 40+/-1 deg C and constant ionic strength (μ = 0.1 M KNO3) in aqueous solution.The stability order was found to be CuII > NiII > CoII > ZnII. pH-metric results were further supported by characterisation of some of the isolated complexes.
- Nagar, Rajesh,Sharma, R. C.
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p. 240 - 242
(2007/10/02)
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