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Research paper thumbnail of Synthesis of microporous polymeric BINOL-derived phosphoric acids and applications in heterogeneous asymmetric organocatalysis

Research paper thumbnail of CCDC 1543566: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Research paper thumbnail of Synthesis of microporous polymeric BINOL-deríved phosphoric acids and applications in hetererogeneous asymmetric organocatalysis

Research paper thumbnail of Organocatalytic Asymmetric Synthesis of 2,3′-Connected Bis-Indolinones by Mannich Reactions of N-Acetylindolin-3-ones with Isatin N-Boc Ketimines

Synthesis, 2017

A highly diastereo- and enantioselective Mannich reaction of N-acetylindolin-3-ones with isatin N... more A highly diastereo- and enantioselective Mannich reaction of N-acetylindolin-3-ones with isatin N-Boc ketimines to form 2,3′-connected bis-indolinones is developed employing a low loading of a readily available bifunctional thiourea catalyst. The asymmetric synthesis connects two indolinones via a vic-diamine unit and generates two neighboring stereocenters.

Research paper thumbnail of One-Pot Synthesis of 1-Substituted 1H-Isochromenes by Combining Brønsted Acid with Silver Catalysis

Synthesis, 2016

A one-pot synthesis of 1-substituted 1H-isochromenes employing various 2-alkynyl-benzaldehydes an... more A one-pot synthesis of 1-substituted 1H-isochromenes employing various 2-alkynyl-benzaldehydes and ketones as substrates under a combination of Brønsted acid and silver catalysis has been developed. The isochromenes, which are present as important heterocyclic core structures in many bioactive and natural compounds, are obtained in medium to excellent yields with diastereomeric ratios of up to 9:1. A first enantioselective variant has also been tested. Key words isochromene, Brønsted acid catalysis, silver catalysis, organocatalysis, one-pot synthesis 12 c Ag 2 CO 3 DPP 40 16 n-hexane 86 13 Ag 2 O DPP 40 16 n-hexane 37 14 AgOTf DPP 40 16 n-hexane 29 15 AgBF 4 DPP 40 16 n-hexane nr 16 AgNO 3 DPP 40 16 n-hexane nr 17 d Ag 2 CO 3 DPP 40 16 n-hexane 93 a Reaction conditions: 1a (0.4 mmol), 2a (0.4 mmol), acid (10 mol%), Ag 2 CO 3 (0.008 mmol), n-hexane (0.3 M, 2.4 mL), 40 °C, 17 h. b Yield of isolated 3a after flash chromatography. c Acetyl acetone (2 equiv) used. d Compound 2a (0.8 mmol), Ag 2 CO 3 (2.5 mol%) used and the concentration reduced to 0.17 M in n-hexane.

Research paper thumbnail of Asymmetric Catalysis of the Carbonyl-Amine Condensation: Kinetic Resolution of Primary Amines

Journal of the American Chemical Society, 2017

A Brønsted acid catalyzed kinetic resolution of primary amines is described that is based on the ... more A Brønsted acid catalyzed kinetic resolution of primary amines is described that is based on the condensation between an amine and a carbonyl compound. 1,3-Diketones react with racemic α-branched amines to furnish the corresponding enantioenriched enaminone and recovered starting material. Good to excellent enantioselectivity was observed with both aromatic and aliphatic primary amines. This process represents the first small-molecule catalyzed kinetic resolution of aliphatic amines.

Research paper thumbnail of N-Arylation of Amides with Cu 2 O Nano-particles

Research paper thumbnail of Reusable Cu2O-Nanoparticle-Catalyzed Amidation of Aryl Iodides

Synlett, 2009

The amidation of aryl iodides using Cu 2 O nanoparticles is described. It is a heterogeneous proc... more The amidation of aryl iodides using Cu 2 O nanoparticles is described. It is a heterogeneous process, no leaching of the Cu 2 O species occurs, and the catalyst can be recovered and recycled without loss of activity.

Research paper thumbnail of Titanium tetrafluoride: An efficient Lewis acid and fluorinating agent for stereoselective synthesis of 4-fluorotetrahydropyran

Journal of Fluorine Chemistry, 2010

Titanium tetrafluoride can efficiently be used for strereoselective synthesis of 4-fluorotetrahyd... more Titanium tetrafluoride can efficiently be used for strereoselective synthesis of 4-fluorotetrahydropyrans via Prins cyclization in good yields. The method is general and can be used for aldehydes as well as ketones.

Research paper thumbnail of Tuning porosity and activity of microporous polymer network organocatalysts by co-polymerisation

Chemical Communications, 2014

Microporous polymer networks based on binaphthyl phosphoric acids are suitable heterogeneous asym... more Microporous polymer networks based on binaphthyl phosphoric acids are suitable heterogeneous asymmetric organocatalysts. Herein we show that the porous characteristics of such networks can be fine-tuned by co-polymerisation. This enables us to investigate the influence of the surface area and porosity in microporous networks on their catalytic performance. In this case, the activity of the polymers in an asymmetric hydrogenation reaction is increased by the use of polymers with higher surface areas. Scheme 1 Monomers used for the co-polymerisation: BNPPA (1) and TTB (2).

Research paper thumbnail of A Microporous Binol-Derived Phosphoric Acid

Angewandte Chemie International Edition, 2012

Dedicated to Professor Ekkehard Winterfeldt on the occasion of his 80th birthday [**] This work w... more Dedicated to Professor Ekkehard Winterfeldt on the occasion of his 80th birthday [**] This work was supported by the Cluster of Excellence "Unifying Concepts in Catalysis" and the "Berlin International Graduate School of Natural Sciences and Engineering". Binol = 1,1'-binaphthalene-2,2'-diol.

Research paper thumbnail of A Chiral Microporous Polymer Network as Asymmetric Heterogeneous Organocatalyst

Advanced Synthesis & Catalysis, 2011

... A Chiral Microporous Polymer Network as Asymmetric Heterogeneous Organocatalyst. Christian Bl... more ... A Chiral Microporous Polymer Network as Asymmetric Heterogeneous Organocatalyst. Christian Bleschke 1 ,; Johannes Schmidt 2,* ,; Dipti S. Kundu 1 ,; Siegfried Blechert 1,* ,; Arne Thomas 2. Article first published online: 16 NOV 2011. ... X. Jiang, A. Cooper, Top. Curr. Chem. Vol ...

Research paper thumbnail of Synthesis of microporous polymeric BINOL-derived phosphoric acids and applications in heterogeneous asymmetric organocatalysis

Research paper thumbnail of CCDC 1543566: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Research paper thumbnail of Synthesis of microporous polymeric BINOL-deríved phosphoric acids and applications in hetererogeneous asymmetric organocatalysis

Research paper thumbnail of Organocatalytic Asymmetric Synthesis of 2,3′-Connected Bis-Indolinones by Mannich Reactions of N-Acetylindolin-3-ones with Isatin N-Boc Ketimines

Synthesis, 2017

A highly diastereo- and enantioselective Mannich reaction of N-acetylindolin-3-ones with isatin N... more A highly diastereo- and enantioselective Mannich reaction of N-acetylindolin-3-ones with isatin N-Boc ketimines to form 2,3′-connected bis-indolinones is developed employing a low loading of a readily available bifunctional thiourea catalyst. The asymmetric synthesis connects two indolinones via a vic-diamine unit and generates two neighboring stereocenters.

Research paper thumbnail of One-Pot Synthesis of 1-Substituted 1H-Isochromenes by Combining Brønsted Acid with Silver Catalysis

Synthesis, 2016

A one-pot synthesis of 1-substituted 1H-isochromenes employing various 2-alkynyl-benzaldehydes an... more A one-pot synthesis of 1-substituted 1H-isochromenes employing various 2-alkynyl-benzaldehydes and ketones as substrates under a combination of Brønsted acid and silver catalysis has been developed. The isochromenes, which are present as important heterocyclic core structures in many bioactive and natural compounds, are obtained in medium to excellent yields with diastereomeric ratios of up to 9:1. A first enantioselective variant has also been tested. Key words isochromene, Brønsted acid catalysis, silver catalysis, organocatalysis, one-pot synthesis 12 c Ag 2 CO 3 DPP 40 16 n-hexane 86 13 Ag 2 O DPP 40 16 n-hexane 37 14 AgOTf DPP 40 16 n-hexane 29 15 AgBF 4 DPP 40 16 n-hexane nr 16 AgNO 3 DPP 40 16 n-hexane nr 17 d Ag 2 CO 3 DPP 40 16 n-hexane 93 a Reaction conditions: 1a (0.4 mmol), 2a (0.4 mmol), acid (10 mol%), Ag 2 CO 3 (0.008 mmol), n-hexane (0.3 M, 2.4 mL), 40 °C, 17 h. b Yield of isolated 3a after flash chromatography. c Acetyl acetone (2 equiv) used. d Compound 2a (0.8 mmol), Ag 2 CO 3 (2.5 mol%) used and the concentration reduced to 0.17 M in n-hexane.

Research paper thumbnail of Asymmetric Catalysis of the Carbonyl-Amine Condensation: Kinetic Resolution of Primary Amines

Journal of the American Chemical Society, 2017

A Brønsted acid catalyzed kinetic resolution of primary amines is described that is based on the ... more A Brønsted acid catalyzed kinetic resolution of primary amines is described that is based on the condensation between an amine and a carbonyl compound. 1,3-Diketones react with racemic α-branched amines to furnish the corresponding enantioenriched enaminone and recovered starting material. Good to excellent enantioselectivity was observed with both aromatic and aliphatic primary amines. This process represents the first small-molecule catalyzed kinetic resolution of aliphatic amines.

Research paper thumbnail of N-Arylation of Amides with Cu 2 O Nano-particles

Research paper thumbnail of Reusable Cu2O-Nanoparticle-Catalyzed Amidation of Aryl Iodides

Synlett, 2009

The amidation of aryl iodides using Cu 2 O nanoparticles is described. It is a heterogeneous proc... more The amidation of aryl iodides using Cu 2 O nanoparticles is described. It is a heterogeneous process, no leaching of the Cu 2 O species occurs, and the catalyst can be recovered and recycled without loss of activity.

Research paper thumbnail of Titanium tetrafluoride: An efficient Lewis acid and fluorinating agent for stereoselective synthesis of 4-fluorotetrahydropyran

Journal of Fluorine Chemistry, 2010

Titanium tetrafluoride can efficiently be used for strereoselective synthesis of 4-fluorotetrahyd... more Titanium tetrafluoride can efficiently be used for strereoselective synthesis of 4-fluorotetrahydropyrans via Prins cyclization in good yields. The method is general and can be used for aldehydes as well as ketones.

Research paper thumbnail of Tuning porosity and activity of microporous polymer network organocatalysts by co-polymerisation

Chemical Communications, 2014

Microporous polymer networks based on binaphthyl phosphoric acids are suitable heterogeneous asym... more Microporous polymer networks based on binaphthyl phosphoric acids are suitable heterogeneous asymmetric organocatalysts. Herein we show that the porous characteristics of such networks can be fine-tuned by co-polymerisation. This enables us to investigate the influence of the surface area and porosity in microporous networks on their catalytic performance. In this case, the activity of the polymers in an asymmetric hydrogenation reaction is increased by the use of polymers with higher surface areas. Scheme 1 Monomers used for the co-polymerisation: BNPPA (1) and TTB (2).

Research paper thumbnail of A Microporous Binol-Derived Phosphoric Acid

Angewandte Chemie International Edition, 2012

Dedicated to Professor Ekkehard Winterfeldt on the occasion of his 80th birthday [**] This work w... more Dedicated to Professor Ekkehard Winterfeldt on the occasion of his 80th birthday [**] This work was supported by the Cluster of Excellence "Unifying Concepts in Catalysis" and the "Berlin International Graduate School of Natural Sciences and Engineering". Binol = 1,1'-binaphthalene-2,2'-diol.

Research paper thumbnail of A Chiral Microporous Polymer Network as Asymmetric Heterogeneous Organocatalyst

Advanced Synthesis & Catalysis, 2011

... A Chiral Microporous Polymer Network as Asymmetric Heterogeneous Organocatalyst. Christian Bl... more ... A Chiral Microporous Polymer Network as Asymmetric Heterogeneous Organocatalyst. Christian Bleschke 1 ,; Johannes Schmidt 2,* ,; Dipti S. Kundu 1 ,; Siegfried Blechert 1,* ,; Arne Thomas 2. Article first published online: 16 NOV 2011. ... X. Jiang, A. Cooper, Top. Curr. Chem. Vol ...