Unusual metal complexes of N,N-bis(2-picolyl)amides – A comparative study of structure and reactivity

Jakob, Uwe; Petersen, Thies Olaf; Bannwarth, Willi

doi:10.1016/j.jorganchem.2015.07.025

Cited by 9 publications

(4 citation statements)

References 35 publications

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“…[24,25] Thep ropensity of amide 1a to undergo quantitative N-or O-coordination with different ligands suggests that selective modification of the amide bond rotational barrier may be possible by using appropriate ligands. [5] As expected, the chemical reactivity of N-alkylated amides is remarkable.Most notably,although the unactivated neutral precursor 1a underwent clean hydrogenation under standard catalytic hydrogenation conditions (H 2 ,P d/C, EtOAc), subjecting the N-methylated lactam 2a to identical hydrogenation conditions afforded the sole product resulting from the cleavage of an otherwise unactivated s CÀNb ond (Scheme 1). [6a] Ther eaction was completely regioselective with respect to the CÀNbond that is more distorted from the C=O p system.…”

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confidence: 57%

“…Over the last three decades,t wisted amides have emerged as valuable transition state mimics of numerous biologically relevant enzymatic reactions. [1][2][3][4] Studies have implicated Ncoordination as am ethod to disrupt the amide bond resonance,w here as uitable ligand activates the amide bond towards isomerization [5] or s N À Cb ond cleavage. [6] The characterization of N-protonated amides represents asignificant challenge because the O-protonated structure is more thermodynamically stable than the N-protonated one (e.g.…”

mentioning

confidence: 99%

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Structural Characterization of N‐Alkylated Twisted Amides: Consequences for Amide Bond Resonance and N−C Cleavage

Lalancette

Szostak

2016

Angew Chem Int Ed

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Herein, we describe the first structural characterization of N-alkylated twisted amides prepared directly by N-alkylation of the corresponding non-planar lactams. This study provides the first experimental evidence that N-alkylation results in a dramatic increase of non-planarity around the amide N-C(O) bond. Moreover, we report a rare example of a molecular wire supported by the same amide C=O-Ag bonds. Reactivity studies demonstrate rapid nucleophilic addition to the N-C(O) moiety of N-alkylated amides, indicating the lack of n(N) to π*(C=O) conjugation. Most crucially, we demonstrate that N-alkylation activates the otherwise unreactive amide bond towards σ N-C cleavage by switchable coordination.

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confidence: 57%

mentioning

confidence: 99%

Structural Characterization of N‐Alkylated Twisted Amides: Consequences for Amide Bond Resonance and N−C Cleavage

Lalancette

Szostak

2016

Angew Chem Int Ed

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“…Ligand coordination increases the rotational barrier (O‐coordination) or disrupts the amide bond resonance (N‐coordination) . Lectka, and Bannwarth, have reported studies on the role of Cu II on the amide bond resonance with multiple binding sites. To date, the effect of N‐/O‐switchable metal coordination on the properties of amides has not been documented.…”

Section: Figurementioning

confidence: 99%

Structural Characterization of N‐Alkylated Twisted Amides: Consequences for Amide Bond Resonance and N−C Cleavage

Lalancette

Szostak

2016

Angewandte Chemie

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Herein, we describe the first structural characterization of N-alkylated twisted amides prepared directly by Nalkylation of the corresponding non-planar lactams.This study provides the first experimental evidence that N-alkylation results in ad ramatic increase of non-planarity around the amide N À C(O) bond. Moreover,w er eport ar are example of amolecular wire supported by the same amide C = O-Ag bonds. Reactivity studies demonstrate rapid nucleophilic addition to the NÀC(O) moiety of N-alkylated amides,indicating the lack of n N to p * C=O conjugation. Most crucially,wedemonstrate that N-alkylation activates the otherwise unreactive amide bond towards s NÀCcleavage by switchable coordination.Over the last three decades,t wisted amides have emerged as valuable transition state mimics of numerous biologically relevant enzymatic reactions. [1][2][3][4] Studies have implicated Ncoordination as am ethod to disrupt the amide bond resonance,w here as uitable ligand activates the amide bond towards isomerization [5] or s N À Cb ond cleavage.[6] The characterization of N-protonated amides represents asignificant challenge because the O-protonated structure is more thermodynamically stable than the N-protonated one (e.g. formamide,1 3.9 kcal mol À1 ); [7] to date only few structural examples of N-protonated amides have been reported (Figure 1A). [8] There is an intrinsic bias favoring N-alkylation vs. O-alkylation by ca. 2.5 kcal mol À1 compared with N-/Oprotonation affinities.[9] O-methylation of dimethylacetamide is favored over N-alkylation by ca. 3kcal mol À1 .[9] N-alkylation of amides plays ac rucial role in av ast range of biologically relevant mechanisms, [10a-g] including enzymatic N-methylation of carboxamido groups, [10a] enzymatic Nalkylation of toxins, [10b] and N-alkylation of polypeptides; [10c] however, the study of N-alkylation of non-planar amides has been severely limited.[11] Alkyl groups exert amore stabilizing effect on the NÀC(O) bond than Hd ue to s C-H to s* N-C hyperconjugation; [12] however, alkyl functions are also more sterically-demanding,w hich contributed to the formidable challenge in straightforward isolation of N-alkylated species. [11] Recently,t here has been as ignificant interest in the activation of NÀC(O) amide bonds by selective metal insertion into the NÀC(O) bond.[13] To date,the vast majority of these transformations involve ag round-state amide distortion [14] such as twisted cyclic imides reported by our group [14a,b,g,h] and acyclic twisted imides reported independently by Zou [14c] and Garg, [14d,e] where N-coordination [7f,g] is believed to activate the amide bond towards metal insertion ( Figure 1B). Moreover,w hile deuterium labeling has been used to investigate mechanisms of amide bond activation, [6a] the NH proton undergoes exchange.T hus,astraightforward access to N-alkylated amides would shed light on the mechanistic details of the NÀCb ond activation reactions.Herein, we demonstrate the first structural characterization of N-alkylated twi...

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“…Macrobicyclic diamides have been used as hosts for cations (Hourdakis & Popov, 1977;Tuemmler et al, 1977;Buschmann, 1986;Rodopoulos et al, 2001;Meyer et al, 2004;Wanichacheva et al, 2006) and anions (Bernier et al, 2009). Tertiary amides have also been shown to form metal complexes (Niklas et al, 2004;Schickaneder et al, 2006;Jakob et al, 2015). The reported compounds,9,10,20,dibenzo [e,q][1,4,10,13,7,16]tetraoxadiazacyclooctadecine-6,13-dione (I), 6,7,9,10,12,13,20,21-octahydro-5,14-(ethanooxyethano)dibenzo [e,q][1,4,10,13,7,16]tetraoxadiazacyclooctadecine-23,27-dione (II), and 9,10,20,21tetrahydro-5,14-(ethanooxyethanooxyethano)dibenzo[e,q]- [1,4,10,13,7,16]tetraoxadiazacyclooctadecine-6,13-dione (III) were synthesized, characterized, and analyzed by X-ray crystallography (Fig.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and structures of three benzoannelated macrobicyclic diamides

Smith

Taylor

2022

Acta Crystallogr C

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We report the synthesis and structures of 9,10,20,21-tetrahydro-5,14-(ethanooxyethano)dibenzo[e,q][1,4,10,13,7,16]tetraoxadiazacyclooctadecine-6,13-dione [systematic name: 8,11,21,24,29-pentaoxa-1,18-diazatetracyclo[16.8.5.02,7.012,17]hentriaconta-2,4,6,12(17),13,15-hexaene-19,26-dione C24H28N2O8, I], 6,7,9,10,12,13,20,21-octahydro-5,14-(ethanooxyethano)dibenzo[e,q][1,4,10,13,7,16]tetraoxadiazacyclooctadecine-23,27-dione (8,11,21,24,29-pentaoxa-1,18-diazatetracyclo[16.8.5.02,7.012,17]hentriaconta-2,4,6,12,14,16-hexaene-27,31-dione; C24H28N2O7, II), and 9,10,20,21-tetrahydro-5,14-(ethanooxyethanooxyethano)dibenzo[e,q][1,4,10,13,7,16]tetraoxadiazacyclooctadecine-6,13-dione [8,11,21,24,29,32-hexaoxa-1,18-diazatetracyclo[16.8.8.02,7.012,17]tetratriaconta-2,4,6,12(17),13,15-hexaene-19,26-dione; C26H32N2O7, III]. All three compounds are made up of two tertiary diamides and are composed of two 15-membered rings with N2O3 donor sets and one 18-membered ring with an N2O4 donor set (compounds I and II) or three 18-membered rings with N2O4 donor sets (compound III). The solid-state structures of compounds I and II show little effects from the movement of the amide groups. However, compound III has a larger cavity and a different orientation of donor atoms in comparison to compounds I and II.

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Unusual metal complexes of N,N-bis(2-picolyl)amides – A comparative study of structure and reactivity

Cited by 9 publications

References 35 publications

Structural Characterization of N‐Alkylated Twisted Amides: Consequences for Amide Bond Resonance and N−C Cleavage

Structural Characterization of N‐Alkylated Twisted Amides: Consequences for Amide Bond Resonance and N−C Cleavage

Structural Characterization of N‐Alkylated Twisted Amides: Consequences for Amide Bond Resonance and N−C Cleavage

Synthesis and structures of three benzoannelated macrobicyclic diamides

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