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4 article(s) from Engeser, Marianne

A heterobimetallic tetrahedron from a linear platinum(II)-bis(acetylide) metalloligand

Matthias Hardy,
Marianne Engeser and
Arne Lützen

Beilstein J. Org. Chem. 2020, 16, 2701–2708, doi:10.3762/bjoc.16.220

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Scheme 1: Stepwise assembly of the heterobimetallic tetrahedron 4, starting from 4-ethynylaniline (1) and tra...

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Figure 1: ESI(+) mass spectrum of heterobimetallic complex 4. The top inset shows the experimentally observed...

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Figure 2: UV–vis spectrum of heterobimetallic complex 4 (1150 µM in acetonitrile at 295 K, 0.01 mm cuvette).

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Figure 3: Schematic representation of symmetry-considerations concerning possible diastereomeric tetrahedra. ...

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Figure 4: Detailed excerpt of the ³¹P NMR spectrum of 4 (202 MHz, acetonitrile-d₃, 298 K).

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Figure 5: ¹H NMR and DOSY spectrum of heterobimetallic assembly 4 (500 MHz, acetonitilre-d₃, 298 K).

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Figure 6: GFN2-xTB minimized gas phase models of the cationic units of all possible diastereomers of 4. Color...

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Published 03 Nov 2020

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Mechanistic studies of an L-proline-catalyzed pyridazine formation involving a Diels–Alder reaction with inverse electron demand

Anne Schnell,
J. Alexander Willms,
S. Nozinovic and
Marianne Engeser

Beilstein J. Org. Chem. 2019, 15, 30–43, doi:10.3762/bjoc.15.3

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Figure 1: Charge-tagged L-proline-derived catalyst 1∙Cl [18].

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Scheme 1: Putative catalytic cycle [51] for the L-proline-catalyzed Diels–Alder reaction with inverse electron de...

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Scheme 2: Synthesis of the charge-tagged tetrazine 4∙Br as a reactant for the proline-catalyzed Diels–Alder r...

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Scheme 3: Reaction R1: L-proline-catalyzed reaction between 2 and acetone.

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Figure 2: NMR monitoring of reaction R1 in deuterated DMSO (concentration of tetrazine 0.005 mmol/mL).

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Scheme 4: Equilibrium of oxazolidinone and enamine formation.

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Figure 3: a) ESI mass spectrum of reaction R1 after 26 min. b) ESIMS monitoring of reaction R1. To better vis...

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Figure 4: ESI mass spectrum of reaction R1 with preformed I₁ 8 minutes after adding substrate 2.

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Scheme 5: Reaction R2: L-proline-catalyzed reaction between charge-tagged substrate 4∙Br and acetone. The reg...

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Figure 5: ESI mass spectrum of reaction R2 using a continuous-flow setup with a calculated reaction time of 8...

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Figure 6: a) Reaction R2 after two hours (syringe setup). b) ESIMS monitoring of reaction R2. Signal intensit...

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Scheme 6: Reaction R3: substrate 2, acetone and charge-tagged catalyst 1∙Cl.

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Figure 7: ESI mass spectrum of reaction R3 at 60 °C after 1.5 h.

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Scheme 7: General catalytic cycle for reactions R1–R3.

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Figure 8: ESIMS monitoring of reaction R3. The plotted intensity values for each molecule are a sum of all co...

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Figure 9: Isomeric forms in equilibrium: enamine [I_3a]⁺, oxazolidinone [I_3b]⁺ and iminium [I_3c]⁺.

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Figure 10: ESI(+) CID spectrum of mass-selected [I₃]⁺ (m/z 353); collision energy voltage 1 V.

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Figure 11: ESI(+) CID spectrum of mass selected [II₃]⁺ (m/z 589); collision energy voltage 5 V.

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Figure 12: ESI(+) CID spectrum of mass selected [III₃]⁺ (m/z 561); collision energy voltage 10 V.

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Published 03 Jan 2019

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A new charge-tagged proline-based organocatalyst for mechanistic studies using electrospray mass spectrometry

J. Alexander Willms,
Rita Beel,
Martin L. Schmidt,
Christian Mundt and
Marianne Engeser

Beilstein J. Org. Chem. 2014, 10, 2027–2037, doi:10.3762/bjoc.10.211

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Figure 1: The new charge-tagged proline-derived catalyst 1.

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Scheme 1: Inverse aldol reaction with aldehyde donors according to Jørgensen [54]. We studied the reaction for R ...

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Scheme 2: Synthesis of 4-(pyridin-4-yl)phenol (5).

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Scheme 3: Synthesis of the charge-tagged proline catalyst 1.

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Figure 2: Molecular structure of 7 in the solid state.

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Scheme 4: Proposed catalytic cycle [36-38] for the aldol reaction with aldehyde donors [54]; CT = charge tag, a: R = Ph, ...

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Figure 3: Experimental setup for continuous-flow ESIMS experiments using two mixing tee microreactors directl...

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Figure 4: ESI mass spectra of acetonitrile solutions of diethyl ketomalonate and butyraldehyde (a) with unmod...

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Figure 5: ESI(+) CID MS/MS spectra of mass-selected intermediates a) [IIb]⁺, b) the butyl ester derivative [I...

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Figure 6: Normalized relative intensities in ESI spectra recorded for the inverse aldol reaction of butyralde...

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Published 28 Aug 2014

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Self-assembly of metallosupramolecular rhombi from chiral concave 9,9’-spirobifluorene-derived bis(pyridine) ligands

Rainer Hovorka,
Sophie Hytteballe,
Torsten Piehler,
Georg Meyer-Eppler,
Filip Topić,
Kari Rissanen,
Marianne Engeser and
Arne Lützen

Beilstein J. Org. Chem. 2014, 10, 432–441, doi:10.3762/bjoc.10.40

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Scheme 1: Synthesis of ligands 3 and 6.

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Figure 1: ESI mass spectrum (positive mode) of an 1:1 mixture of (R)-3 and [(dppp)Pd(OTf)₂] in acetone.

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Figure 2: ¹H NMR spectra (500.1 MHz, in CD₂Cl₂/CD₃CN 3:1 at 298 K) of a) a 1:1 mixture of [Pd(dppp)]OTf₂ and (...

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Figure 3: ³¹P NMR spectra of a) a 1:1 mixture of [Pd(dppp)]OTf₂ and (R)-3, b) a 1:1 mixture of [Pd(dppp)]OTf₂...

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Figure 4: ESI mass spectrum (positive mode) of an 1:1:2 mixture of (R)-3, (S)-6, and [(dppp)Pt(OTf)₂] in acet...

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Figure 5: Single crystal X-ray structure analysis of [(dppp)₂Pd₂{(R)-3}₂][(dppp)₂Pd₂{(S)-3}₂](OTf)₈ obtained ...

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Published 18 Feb 2014

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