Search results for: Marc Schmidtmann

Items from 1 to 20 out of 112 results

article

Synthetic Studies towards Pheromones by Cyanide‐Catalyzed Ring Transformation of α‐Hydroxy‐β‐oxoesters to δ‐Valerolactones

Jean‐Marico Speldrich, Marc Schmidtmann, Jens Christoffers

European Journal of Organic Chemistry > 26 > 8 > n/a - n/a

The cyanide‐catalyzed ring‐transformation of α‐hydroxy‐β‐oxoesters to δ‐lactones with exocyclic ester moiety is the key transformation for the preparation of racemic 5‐hexadecanolide (15 % over nine steps) and 6‐acetoxy‐5‐hexadecanolide (22 % over eight steps), two insect pheromones. The benzyloxycarbonyl moiety is transformed via the acid chloride to the undecanoyl side chain. After reduction of...

article

Synthesis of Flavin‐Indole Conjugates with Rigid Diamino Linkers as Cryptochrome Model Compounds

Nils Schröder, Marc Schmidtmann, Henrik Mouritsen, Jens Christoffers

European Journal of Organic Chemistry > 26 > 7 > n/a - n/a

The synthesis of flavin‐indole conjugates with a trans‐1,4‐diaminocyclohexane and a 2,6‐diaminodecahydronaphthalene linker is reported. Both compounds should serve as artificial model compounds for natural cryptochrome. It is assumed that cryptochrome photoreceptor proteins located in the retina show a light‐dependent quantum effect which enables migratory birds to perceive the Earth's magnetic field...

article

Niobium Bis‐ and Mono(Pentafulvene) Complexes: E−H Bond Cleavage and Insertion Reactions (E=C, N, O)

Simon Graaff, Marcel Eilers, Julia Buschermöhle, Nina Bengen, more

European Journal of Inorganic Chemistry > 26 > 5 > n/a - n/a

Bis(η⁵:η¹‐(di‐para‐tolyl)pentafulvene)niobium chloride (1) reacts with methyl lithium via salt metathesis to the methylated bis(pentafulvene)niobium complex 2, and with lithium 2,6‐diisopropylanilide addition and subsequent N−H bond activation to the imido mono(pentafulvene)niobium complex 3. Avoiding the competing protonation of the chloride, bis(pentafulvene)niobium complex 2 reacts with primary...

article

Cover Feature: Titanium‐Catalyzed Intermolecular Hydroaminoalkylation of Allenes and Methylenecyclopropanes (Eur. J. Org. Chem. 45/2022)

Tobias Kaper, Aylişa Elma, Hermann Thye, Paula Knupe‐Wolfgang, more

European Journal of Organic Chemistry > 2022 > 45 > n/a - n/a

The Cover Feature illustrates the titanium‐catalyzed α‐functionalization of secondary amines with either allenes or methylenecyclopropanes. To achieve this, the employed catalyst must act like a wizard, miraculously activating C−H bonds and thereby combining the starting materials regio‐ and stereoselectively. Cover design by Melissa Schlüschen. More information can be found in the Research Article...

article

Titanium‐Catalyzed Intermolecular Hydroaminoalkylation of Allenes and Methylenecyclopropanes

Tobias Kaper, Aylişa Elma, Hermann Thye, Paula Knupe‐Wolfgang, more

European Journal of Organic Chemistry > 2022 > 45 > n/a - n/a

Intermolecular hydroaminoalkylation reactions of 1,1‐ and 1,3‐disubstituted allenes as well as methylenecyclopropanes with secondary amines can be achieved in the presence of a 2,6‐bis(phenylamino)pyridinato titanium catalyst at 140 °C within 2–8 h. Corresponding reactions of allenes with N‐benzylanilines deliver branched allylamine products in very good yields (up to 83 %) and with branched‐linear‐ratios...

article

Stereoselective Synthesis of Tertiary Allylic Amines by Titanium‐Catalyzed Hydroaminoalkylation of Alkynes with Tertiary Amines

Tobias Kaper, Dennis Geik, Felix Fornfeist, Marc Schmidtmann, more

Chemistry – A European Journal > 28 > 10 > n/a - n/a

Intermolecular hydroaminoalkylation reactions of symmetrical and unsymmetrical alkynes with tertiary amines take place in the presence of catalytic amounts of TiBn₄, Ph₃C[B(C₆F₅)₄], and a sterically demanding aminopyridinato ligand precursor. The resulting products, synthetically and pharmaceutically useful tertiary β,γ‐disubstituted allylic amines, are formed in convincing yields and with excellent...

article

Radicals and Anions of Siloles and Germoles

Crispin R. W. Reinhold, Marc Schmidtmann, Boris Tumanskii, Thomas Müller

Chemistry – A European Journal > 27 > 47 > 12063 - 12068

The synthesis of persistent sila‐ and germacyclopentadienyl (silolyl‐ and germolyl‐) radicals by careful stoichiometric reduction of the corresponding halides with potassium is reported. The radicals were characterized by EPR spectroscopy and trapping reactions. The reduction of tris(trimethylsilyl)silyl‐substituted halides was successful while smaller substituents (i. e., t‐Butyl, Ph) gave the corresponding...

article

Radicals and Anions of Siloles and Germoles

Crispin R. W. Reinhold, Marc Schmidtmann, Boris Tumanskii, Thomas Müller

Chemistry – A European Journal > 27 > 47 > 12011 - 12011

Invited for the cover of this issue is the group of Thomas Müller at the University of Oldenburg. The image shows the calculated spin distribution of a persistent silacyclopentadienyl radical. Read the full text of the article at 10.1002/chem.202101415.

article

Front Cover: Radicals and Anions of Siloles and Germoles (Chem. Eur. J. 47/2021)

Crispin R. W. Reinhold, Marc Schmidtmann, Boris Tumanskii, Thomas Müller

Chemistry – A European Journal > 27 > 47 > 12007 - 12007

The synthesis of sterically hindered persistent sila‐ and germacyclopentadienyl radicals adds magnetic properties to these heterocyclic ring systems and sparks the idea of their possible application as building blocks for molecular magnets (pictured as red‐blueish northern light). Support comes from the analysis of the EPR spectroscopic parameters and of their computed spin density ‐ shown here for...

article

Diaminoterephthalate‐EDTA and ‐EGTA Conjugates – “Turn on” Fluorescence Sensors for Zinc Ions

Nils Schröder, Marc Schmidtmann, Jens Christoffers

European Journal of Organic Chemistry > 2021 > 30 > 4260 - 4268

A highly effective “turn‐on” fluorescence sensor with high selectivity for Zn²⁺ ions is reported. Its constitution simply consists of two units of the fluorescence dye diaminoterephthalate (DAT) and the chelate ligand EDTA. In total, four products (DAT)₂EDTA and (DAT)₂EGTA were prepared by conjugation of DATs with chelate ligands EDTA and EGTA as sensors for metal ions in solution. The fluorescence...

article

Cover Feature: Diaminoterephthalate‐EDTA and ‐EGTA Conjugates – “Turn on” Fluorescence Sensors for Zinc Ions (Eur. J. Org. Chem. 30/2021)

Nils Schröder, Marc Schmidtmann, Jens Christoffers

European Journal of Organic Chemistry > 2021 > 30 > 4244 - 4244

The Cover Feature shows how the crab chelates the zinc ion with its claws. The crab represents the constitutionally very simple sensor (DAT)₂EDTA with remarkable selectivity towards Zn²⁺ ions. This molecular sensor was obtained by conjugation of the fluorescence dye diaminoterephthalate (DAT) with the chelator EDTA by amide formation. The fluorescence quantum yield of the DAT chromophore is increased...

article

Titanium‐Catalyzed Intermolecular Hydroaminoalkylation of Alkenes with Tertiary Amines

Dennis Geik, Michael Rosien, Jens Bielefeld, Marc Schmidtmann, more

Angewandte Chemie International Edition > 60 > 18 > 9936 - 9940

The first cationic titanium catalyst system for the intermolecular hydroaminoalkylation of alkenes with various tertiary alkylamines is presented. Corresponding reactions which involve the addition of the α‐C−H bond of a tertiary amine across the C−C double bond of an alkene take place at temperatures close to room temperature with excellent regioselectivity to deliver the branched products exclusively...

article

Cover Feature: Intermolecular Hydroaminoalkylation of Alkynes (Chem. Eur. J. 23/2021)

Tobias Kaper, Malte Fischer, Hermann Thye, Dennis Geik, more

Chemistry – A European Journal > 27 > 23 > 6817 - 6817

Hydroaminoalkylation! In this work, the conversion of alkynes into allylic amines within an unbelievably short reaction time of 4 h is presented. In addition to the fast reaction, hydroaminoalkylation is promoted by broad scope, high yields, and excellent stereoselectivity to provide access to synthetically useful products in record time. More information can be found in the Communication by R. Beckhaus,...

article

Intermolecular Hydroaminoalkylation of Alkynes

Tobias Kaper, Malte Fischer, Hermann Thye, Dennis Geik, more

Chemistry – A European Journal > 27 > 23 > 6899 - 6903

Intermolecular hydroaminoalkylation reactions of alkynes with secondary amines, which selectively give access to allylic amines with E configuration of the alkene unit, are achieved in the presence of titanium catalysts. Successful reactions of symmetrically substituted diaryl‐ and dialkylalkynes as well as a terminal alkyne take place with N‐benzylanilines, N‐alkylanilines, and N‐alkylbenzylamines.

article

Titanium‐Catalyzed Intermolecular Hydroaminoalkylation of Alkenes with Tertiary Amines

Dennis Geik, Michael Rosien, Jens Bielefeld, Marc Schmidtmann, more

Angewandte Chemie > 133 > 18 > 10024 - 10028

article

Intramolecular Halo Stabilization of Silyl Cations—Silylated Halonium‐ and Bis‐Halo‐Substituted Siliconium Borates

Anastasia Merk, Lukas Bührmann, Natalie Kordts, Katharina Görtemaker, more

Chemistry – A European Journal > 27 > 10 > 3496 - 3503

The stabilizing neighboring effect of halo substituents on silyl cations was tested for a series of peri‐halo substituted acenaphthyl‐based silyl cations 3. The chloro‐ (3 b), bromo‐ (3 c), and iodo‐ (3 d) stabilized cations were synthesized by the Corey protocol. Structural and NMR spectroscopic investigations for cations 3 b–d supported by the results of density functional calculations, which indicate...

article

Hydroaminoalkylation/Buchwald‐Hartwig Amination Sequences for the Synthesis of Novel Thieno‐ or Benzothieno‐Annulated Tetrahydropyridines, Tetrahydroazasilines, and Tetrahydroazasilepines

Michael Warsitz, Stefan H. Rohjans, Marc Schmidtmann, Sven Doye

European Journal of Organic Chemistry > 2021 > 5 > 830 - 849

New two‐step procedures that include an initial regioselective intermolecular hydroaminoalkylation of 2‐allyl‐, 2‐allyldimethylsilyl‐, or 2‐dimethyl(vinyl)silyl‐substituted 3‐bromothiophenes or 3‐bromobenzothiophenes with secondary amines and a subsequent intramolecular Buchwald‐Hartwig amination give direct access to structurally novel bicyclic heterocycles including tetrahydrothienopyridines, tetrahydrothienoazasilines,...

article

Chiral Chalcogenyl‐Substituted Naphthyl‐ and Acenaphthyl‐Silanes and Their Cations

Sandra Künzler, Saskia Rathjen, Katherina Rüger, Marie S. Würdemann, more

Chemistry – A European Journal > 26 > 69 > 16441 - 16449

Cyclic silylated chalconium borates 13[B(C₆F₅)₄] and 14[B(C₆F₅)₄] with peri‐acenaphthyl and peri‐naphthyl skeletons were synthesized from unsymmetrically substituted silanes 3, 4, 6, 7, 9 and 10 using the standard Corey protocol (Chalcogen Ch=O, S, Se, Te). The configuration at the chalcogen atom is trigonal pyramidal for Ch=S, Se, Te, leading to the formation of cis‐ and trans‐isomers in the case...

article

Preparation of Hexahydrocarbazole Derivatives by Reductive Indolization

Anna Dierks, Lukas Fliegel, Marc Schmidtmann, Jens Christoffers

European Journal of Organic Chemistry > 2020 > 46 > 7164 - 7175

The reductive indolization is a two‐step protocol performed in one flask: First, the acid‐mediated Fischer indolization of a cyclic ketone with phenylhydrazine forms an iminium ion which is subsequently reduced by a hydrido borate reagent to the indoline as the final product. We utilized this new strategy for the preparation of hexahydrocarbazole derivatives with a side chain in the quaternary C4a‐position...

article

Front Cover: Tris(dicyclohexylamido) Group 4 Metal Allyl and Phenylacetylide Complexes – Synthesis and Characterization (Eur. J. Inorg. Chem. 45/2020)

Nils Frerichs, Lenard Lukas, Marc Schmidtmann, Rüdiger Beckhaus

European Journal of Inorganic Chemistry > 2020 > 45 > 4236 - 4236

The Front Cover shows a combination of the molecular structures of selected group 4 metal compounds discussed in the article and windmills characteristic to the landscape of our region in Northern Germany. Together with the investigated allyl and phenylacetylide ligands, the central metal atoms form the hub of the wind turbines. The blades symbolize the bond between the metal atom and the amido ligands,...

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Search results for: Marc Schmidtmann

Synthetic Studies towards Pheromones by Cyanide‐Catalyzed Ring Transformation of α‐Hydroxy‐β‐oxoesters to δ‐Valerolactones

Synthesis of Flavin‐Indole Conjugates with Rigid Diamino Linkers as Cryptochrome Model Compounds

Niobium Bis‐ and Mono(Pentafulvene) Complexes: E−H Bond Cleavage and Insertion Reactions (E=C, N, O)

Cover Feature: Titanium‐Catalyzed Intermolecular Hydroaminoalkylation of Allenes and Methylenecyclopropanes (Eur. J. Org. Chem. 45/2022)

Titanium‐Catalyzed Intermolecular Hydroaminoalkylation of Allenes and Methylenecyclopropanes

Stereoselective Synthesis of Tertiary Allylic Amines by Titanium‐Catalyzed Hydroaminoalkylation of Alkynes with Tertiary Amines

Radicals and Anions of Siloles and Germoles

Radicals and Anions of Siloles and Germoles

Front Cover: Radicals and Anions of Siloles and Germoles (Chem. Eur. J. 47/2021)

Diaminoterephthalate‐EDTA and ‐EGTA Conjugates – “Turn on” Fluorescence Sensors for Zinc Ions

Cover Feature: Diaminoterephthalate‐EDTA and ‐EGTA Conjugates – “Turn on” Fluorescence Sensors for Zinc Ions (Eur. J. Org. Chem. 30/2021)

Titanium‐Catalyzed Intermolecular Hydroaminoalkylation of Alkenes with Tertiary Amines

Cover Feature: Intermolecular Hydroaminoalkylation of Alkynes (Chem. Eur. J. 23/2021)

Intermolecular Hydroaminoalkylation of Alkynes

Titanium‐Catalyzed Intermolecular Hydroaminoalkylation of Alkenes with Tertiary Amines

Intramolecular Halo Stabilization of Silyl Cations—Silylated Halonium‐ and Bis‐Halo‐Substituted Siliconium Borates

Hydroaminoalkylation/Buchwald‐Hartwig Amination Sequences for the Synthesis of Novel Thieno‐ or Benzothieno‐Annulated Tetrahydropyridines, Tetrahydroazasilines, and Tetrahydroazasilepines

Chiral Chalcogenyl‐Substituted Naphthyl‐ and Acenaphthyl‐Silanes and Their Cations

Preparation of Hexahydrocarbazole Derivatives by Reductive Indolization

Front Cover: Tris(dicyclohexylamido) Group 4 Metal Allyl and Phenylacetylide Complexes – Synthesis and Characterization (Eur. J. Inorg. Chem. 45/2020)

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