α-Bromodiazoacetamides – a new class of diazo compounds for catalyst-free, ambient temperature intramolecular C–H insertion reactions

Kaupang, Åsmund; Bonge‐Hansen, Tore

doi:10.3762/bjoc.9.157

Cited by 27 publications

(13 citation statements)

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“…A similar overall yield (57%) was obtained by Delgado et al by alkylation with ethyl bromoacetate in ethanol using trimethylamine as a base and subsequent hydrolysis in water [ 28 ]. t O2DO2AM Pip was obtained by alkylating the parent macrocycle with 2-bromo-1-(piperidin-1-yl)ethan-1-one, synthesized according to published procedures [ 29 ], in the presence of K 2 CO 3 as a base. The ligand used in the studies was purified by preparative HPLC (High-Performance Liquid Chromatography) on a Luna 10u-Prep C18(2) 100 A (250 × 21.20 mm) column, using MeCN/0.005 M TFA in H 2 O as the eluent.…”

Section: Resultsmentioning

confidence: 99%

“…All reagents were obtained from commercial sources and were used as received. The 1,7-diaza-12-crown-4 macrocycle was purchased from the CheMatech (Dijon, France) whereas the 2-bromo-1-(piperidin-1-yl)ethan-1-one was synthesized by following the published procedure [ 29 ]. Solvents were of reagent grade and were used without further purification.…”

Section: Methodsmentioning

confidence: 99%

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Expanding the Ligand Classes Used for Mn(II) Complexation: Oxa-aza Macrocycles Make the Difference

et al. 2021

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We report two macrocyclic ligands based on a 1,7-diaza-12-crown-4 platform functionalized with acetate (tO2DO2A2−) or piperidineacetamide (tO2DO2AMPip) pendant arms and a detailed characterization of the corresponding Mn(II) complexes. The X−ray structure of [Mn(tO2DO2A)(H2O)]·2H2O shows that the metal ion is coordinated by six donor atoms of the macrocyclic ligand and one water molecule, to result in seven-coordination. The Cu(II) analogue presents a distorted octahedral coordination environment. The protonation constants of the ligands and the stability constants of the complexes formed with Mn(II) and other biologically relevant metal ions (Mg(II), Ca(II), Cu(II) and Zn(II)) were determined using potentiometric titrations (I = 0.15 M NaCl, T = 25 °C). The conditional stabilities of Mn(II) complexes at pH 7.4 are comparable to those reported for the cyclen-based tDO2A2− ligand. The dissociation of the Mn(II) chelates were investigated by evaluating the rate constants of metal exchange reactions with Cu(II) under acidic conditions (I = 0.15 M NaCl, T = 25 °C). Dissociation of the [Mn(tO2DO2A)(H2O)] complex occurs through both proton− and metal−assisted pathways, while the [Mn(tO2DO2AMPip)(H2O)] analogue dissociates through spontaneous and proton-assisted mechanisms. The Mn(II) complex of tO2DO2A2− is remarkably inert with respect to its dissociation, while the amide analogue is significantly more labile. The presence of a water molecule coordinated to Mn(II) imparts relatively high relaxivities to the complexes. The parameters determining this key property were investigated using 17O NMR (Nuclear Magnetic Resonance) transverse relaxation rates and 1H nuclear magnetic relaxation dispersion (NMRD) profiles.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Expanding the Ligand Classes Used for Mn(II) Complexation: Oxa-aza Macrocycles Make the Difference

et al. 2021

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“…The ligands were either prepared by following literature procedures (DOTAM, DO3A, DO3P, PCTA, ODO3A, PC3AM Gly ) (Amorim et al, 1988 ; Maumela et al, 1995 ; Aime et al, 1997 ; Siaugue et al, 2000 ; Sun et al, 2003 ; Rojas-Quijano et al, 2009 ; Nithyakumar and Alexander, 2016 ) or obtained from commercial sources (DO3AM H - CheMatech, Dijon (France)). The PC3AM H and PC3AM Pip ligands were prepared by alkylating the pyclen macrocycle prepared according to literature description (Stetter et al, 1981 ) with a suitable bromoacetamide derivative (see the Supplementary Material for the detailed synthesis and analytical data) available from commercial sources or prepared by following literature synthesis (Kaupang and Bonge-Hansen, 2013 ).…”

Section: Methodsmentioning

confidence: 99%

Effect of the Nature of Donor Atoms on the Thermodynamic, Kinetic and Relaxation Properties of Mn(II) Complexes Formed With Some Trisubstituted 12-Membered Macrocyclic Ligands

et al. 2018

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During the past few years increasing attention has been devoted to Mn(II) complexes as possible substitutes for Gd(III) complexes as contrast agents in MRI. Equilibrium (log KMnL or pMn value), kinetic parameters (rates and half-lives of dissociation) and relaxivity of the Mn(II) complexes formed with 12-membered macrocyclic ligands were studied. The ligands were selected in a way to gain information on how the ligand rigidity, the nature of the donor atoms in the macrocycle (pyridine N, amine N, and etheric O atom), the nature of the pendant arms (carboxylates, phosphonates, primary, secondary and tertiary amides) affect the physicochemical parameters of the Mn(II) complexes. As expected, decreasing the denticity of DOTA (to afford DO3A) resulted in a drop in the stability and inertness of [Mn(DO3A)]− compared to [Mn(DOTA)]2−. This decrease can be compensated partially by incorporating the fourth nitrogen atom into a pyridine ring (e.g., PCTA) or by replacement with an etheric oxygen atom (ODO3A). Moreover, the substitution of primary amides for acetates resulted in a noticeable drop in the stability constant (PC3AMH), but it increased as the primary amides (PC3AMH) were replaced by secondary (PC3AMGly) or tertiary amide (PC3AMPip) pendants. The inertness of the Mn(II) complexes behaved alike as the rates of acid catalyzed dissociation increased going from DOTA (k1 = 0.040 M−1s−1) to DO3A (k1 = 0.45 M−1s−1). However, the rates of acid catalyzed dissociation decreased from 0.112 M−1s−1 observed for the anionic Mn(II) complex of PCTA to 0.0107 M−1s−1 and 0.00458 M−1s−1 for the cationic Mn(II) complexes of PC3AMH and PC3AMPip ligands, respectively. In spite of its lower denticity (as compared to DOTA) the sterically more hindered amide complex ([Mn(PC3AMPip)]2+) displays surprisingly high conditional stability (pMn = 8.86 vs. pMn = 9.74 for [Mn(PCTA)]−) and excellent kinetic inertness. The substitution of phosphonates for the acetate pendant arms (DOTP and DO3P), however, resulted in a noticeable drop in the conditional stability as well as dissociation kinetic parameters of the corresponding Mn(II) complexes ([Mn(DOTP)]6− and [Mn(DO3P)]4−) underlining that the phosphonate pedant should not be considered as a suitable building block for further ligand design while the tertiary amide moiety will likely have some implications in this respect in the future.

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“…For normal bond lengths in organic compounds, see: Allen et al (1987). For synthetic details, see: Kaupang & Bonge-Hansen (2013); Kaupang (2010); Toma et al (2007). For the synthesis of other diazoacetamides with a 1,4-diaza six-membered ring, see: Kaupang (2010); Mickelson et al (1996).…”

Section: Related Literaturementioning

confidence: 99%

1,4-Bis(2-diazoacetyl)piperazine

Kaupang¹,

Görbitz²,

Bonge‐Hansen³

2013

Acta Cryst E

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The asymmetric unit of the title compound, C8H10N6O2, contains one-half molecule, which is completed by a crystallographic center of symmetry. The piperazine ring adopts a chair conformation. In the crystal, weak C—H⋯O interactions link the molecules into layers parallel to the bc plane. The crystal packing also exhibits short N⋯N contacts of 3.0467 (16) Å between the terminal diazo N atoms from neighbouring molecules.

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α-Bromodiazoacetamides – a new class of diazo compounds for catalyst-free, ambient temperature intramolecular C–H insertion reactions

Cited by 27 publications

References 83 publications

Expanding the Ligand Classes Used for Mn(II) Complexation: Oxa-aza Macrocycles Make the Difference

Expanding the Ligand Classes Used for Mn(II) Complexation: Oxa-aza Macrocycles Make the Difference

Effect of the Nature of Donor Atoms on the Thermodynamic, Kinetic and Relaxation Properties of Mn(II) Complexes Formed With Some Trisubstituted 12-Membered Macrocyclic Ligands

1,4-Bis(2-diazoacetyl)piperazine

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