scholarly journals A Commercially Available Ruthenium Compound for Catalytic Hydrophosphination

2019 ◽  
Author(s):  
Michael P. Cibuzar ◽  
Steven G. Danneberg ◽  
Rory Waterman
Keyword(s):  
Ruthenium Compound ◽  
Michael Acceptors ◽  
Styrene Derivatives ◽  
Catalyzed Reactions ◽  
Secondary Phosphines

Hydrophosphination with a commercially available ruthenium compound, bis(cyclopentadienylruthenium dicarbonyl) dimer ([CpRu(CO)2]2), was explored. Styrene derivatives or Michael acceptors react readily with either primary or secondary phosphines in the presence of 0.1 mol% of [CpRu(CO)2]2 under photolysis with an inexpensive and commercially available UV-A 9W lamp. In comparison to related photoactivated hydrophosphination reactions with [CpFe(CO)2]2 as a catalyst, these ruthenium-catalyzed reactions proceed at greater relative rates with lower catalyst loadings. <br>

scholarly journals A Commercially Available Ruthenium Compound for Catalytic Hydrophosphination

2019 ◽  
Author(s):  
Michael P. Cibuzar ◽  
Steven G. Danneberg ◽  
Rory Waterman
Keyword(s):  
Ruthenium Compound ◽  
Michael Acceptors ◽  
Styrene Derivatives ◽  
Catalyzed Reactions ◽  
Secondary Phosphines

Hydrophosphination with a commercially available ruthenium compound, bis(cyclopentadienylruthenium dicarbonyl) dimer ([CpRu(CO)2]2), was explored. Styrene derivatives or Michael acceptors react readily with either primary or secondary phosphines in the presence of 0.1 mol% of [CpRu(CO)2]2 under photolysis with an inexpensive and commercially available UV-A 9W lamp. In comparison to related photoactivated hydrophosphination reactions with [CpFe(CO)2]2 as a catalyst, these ruthenium-catalyzed reactions proceed at greater relative rates with lower catalyst loadings. <br>

Anionic Cyclometallated platinum(II) Tetrazolato Complexes as Viable Photoredox Catalysts

2018 ◽  
Author(s):  
Anna Maria Ranieri ◽  
Liam Burt ◽  
Stefano Stagni ◽  
Stefano Zacchini ◽  
Brian Skelton ◽  
...  
Keyword(s):  
Solid State ◽  
Visible Light ◽  
Room Temperature ◽  
Functional Group ◽  
Photophysical Properties ◽  
General Structure ◽  
No Emission ◽  
Michael Acceptors ◽  
Catalyzed Reactions

The synthesis, characterization, photophysical and photocatalytic studies of anionic platinum(II) tetrazolato complexes, with the general structure [TBA][Pt(CNC)TzR], are reported, where CNC<sup>2-</sup>represents a doubly cyclometalated 2,4,6-triphenylpyridine, TzR<sup>- </sup>is an anionic 5-substituted tetrazolato ligand (with a variable R functional group) and TBA<sup>+ </sup>is the tetrabutylammonium countercation. The complexes were prepared by substitution of the DMSO ligand in [Pt(CNC)(DMSO)] with the corresponding tetrazolato ligand. No emission from the platinum(II) complexes was detected at room temperature in solution, but the photophysical properties could be assessed in the solid state, where all the complexes display emission bands attributed to aggregates. The platinum(II) complexes were found to facilitate a range of fundamental classes of visible-light-mediated photoredox-catalyzed reactions, including α‑amino C–H functionalization processes, such as Povarov-type reactions and the addition of α-amino C–H bonds across Michael acceptors, in addition to ATRA chemistry, and a hydrodeiodination. With the exception of the hydrodeiodination process, the best Pt(II) catalysts provided turnover numbers of 150–175 in each of these transformations.

scholarly journals Copper-mediated asymmetric transformations

2002 ◽  
Vol 74 (1) ◽  
pp. 37-42 ◽  
Author(s):  
Alexandre Alexakis
Keyword(s):  
Conjugate Addition ◽  
Organometallic Reagent ◽  
Asymmetric Transformations ◽  
Michael Acceptors ◽  
Catalyzed Reactions ◽  
Zinc Enolate

Copper-catalyzed reactions include the enantioselective conjugate addition and the SN2¢ substitution. We describe the genesis of these reactions, the choice of the primary organometallic reagent, and our studies on finding new Michael acceptors and new ligands. We also report on the use of the zinc enolate generated upon conjugate addition.

Anionic Cyclometallated platinum(II) Tetrazolato Complexes as Viable Photoredox Catalysts

2018 ◽  
Author(s):  
Anna Maria Ranieri ◽  
Liam Burt ◽  
Stefano Stagni ◽  
Stefano Zacchini ◽  
Brian Skelton ◽  
...  
Keyword(s):  
Solid State ◽  
Visible Light ◽  
Room Temperature ◽  
Functional Group ◽  
Photophysical Properties ◽  
General Structure ◽  
No Emission ◽  
Michael Acceptors ◽  
Catalyzed Reactions

The synthesis, characterization, photophysical and photocatalytic studies of anionic platinum(II) tetrazolato complexes, with the general structure [TBA][Pt(CNC)TzR], are reported, where CNC<sup>2-</sup>represents a doubly cyclometalated 2,4,6-triphenylpyridine, TzR<sup>- </sup>is an anionic 5-substituted tetrazolato ligand (with a variable R functional group) and TBA<sup>+ </sup>is the tetrabutylammonium countercation. The complexes were prepared by substitution of the DMSO ligand in [Pt(CNC)(DMSO)] with the corresponding tetrazolato ligand. No emission from the platinum(II) complexes was detected at room temperature in solution, but the photophysical properties could be assessed in the solid state, where all the complexes display emission bands attributed to aggregates. The platinum(II) complexes were found to facilitate a range of fundamental classes of visible-light-mediated photoredox-catalyzed reactions, including α‑amino C–H functionalization processes, such as Povarov-type reactions and the addition of α-amino C–H bonds across Michael acceptors, in addition to ATRA chemistry, and a hydrodeiodination. With the exception of the hydrodeiodination process, the best Pt(II) catalysts provided turnover numbers of 150–175 in each of these transformations.

A kinetic analysis of coupled sequential enzyme reactions

2018 ◽  
Author(s):  
Justin Eilertsen ◽  
Santiago Schnell
Keyword(s):  
Enzyme Assay ◽  
Sequential Reaction ◽  
Enzyme Reactions ◽  
Indicator Reaction ◽  
Single Substrate ◽  
Complex Sequences ◽  
Catalyzed Reactions ◽  
Enzyme Catalyzed Reactions ◽  
Single Enzyme

<div>As a case study, we consider a coupled enzyme assay of sequential enzyme reactions obeying the Michaelis--Menten reaction mechanism. The sequential reaction consists of a single-substrate, single-enzyme non-observable reaction followed by another single-substrate, single-enzyme observable reaction (indicator reaction). In this assay, the product of the non-observable reaction becomes the substrate of the indicator reaction. A mathematical analysis of the reaction kinetics is performed, and it is found that after an initial fast transient, the sequential reaction is described by a pair of interacting Michaelis--Menten equations. Timescales that approximate the respective lengths of the indicator and non-observable reactions, as well as conditions for the validity of the Michaelis--Menten equations are derived. The theory can be extended to deal with more complex sequences of enzyme catalyzed reactions.</div>

A kinetic analysis of coupled sequential enzyme reactions

2018 ◽  
Author(s):  
Justin Eilertsen ◽  
Santiago Schnell
Keyword(s):  
Enzyme Assay ◽  
Sequential Reaction ◽  
Enzyme Reactions ◽  
Indicator Reaction ◽  
Single Substrate ◽  
Complex Sequences ◽  
Catalyzed Reactions ◽  
Enzyme Catalyzed Reactions ◽  
Single Enzyme

<div>As a case study, we consider a coupled enzyme assay of sequential enzyme reactions obeying the Michaelis-Menten reaction mechanism. The sequential reaction consists of a single-substrate, single enzyme non-observable reaction followed by another single-substrate, single enzyme observable reaction (indicator reaction). In this assay, the product of the non-observable reaction becomes the substrate of the indicator reaction. A mathematical analysis of the reaction kinetics is performed, and it is found that after an initial fast transient, the sequential reaction is described by a pair of interacting Michaelis-Menten equations. Timescales that approximate the respective lengths of the indicator and non-observable reactions, as well as conditions for the validity of the Michaelis-Menten equations are derived. The theory can be extended to deal with more complex sequences of enzyme catalyzed reactions.</div>

Visible Light-Induced Sulfonylation/Arylation of Styrenes in a Double Radical Three-Component Photoredox Reaction

2019 ◽  
Author(s):  
Benjamin Lipp ◽  
Lisa Marie Kammer ◽  
Murat Kucukdisli ◽  
Adriana Luque ◽  
Jonas Kühlborn ◽  
...  
Keyword(s):  
Visible Light ◽  
Radical Formation ◽  
Three Component Reaction ◽  
Broad Variety ◽  
Styrene Derivatives ◽  
Mechanistic Investigations

Simultaneous sulfonylation/arylation of styrene derivatives is achieved in a photoredox-catalyzed three-component reaction using visible light. A broad variety of difunctionalized products is accessible in mostly excellent yields and high diastereoselectivity. The developed reaction is scalable and suitable for the modification of styrene-functionalized biomolecules. Mechanistic investigations suggest the transformation to be operating through a designed sequence of radical formation and radical combination.<br>

Computationally Augmented Retrosynthesis: Total Synthesis of Paspaline A and Emindole PB

2018 ◽  
Author(s):  
Timothy Newhouse ◽  
Daria E. Kim ◽  
Joshua E. Zweig
Keyword(s):  
Chemical Synthesis ◽  
Total Synthesis ◽  
Small Molecules ◽  
First Principles ◽  
Quantum Chemical ◽  
Computational Analysis ◽  
Empirical Evaluation ◽  
Synthetic Strategy ◽  
Catalyzed Reactions ◽  
Enzyme Catalyzed Reactions

The diverse molecular architectures of terpene natural products are assembled by exquisite enzyme-catalyzed reactions. Successful recapitulation of these transformations using chemical synthesis is hard to predict from first principles and therefore challenging to execute. A means of evaluating the feasibility of such chemical reactions would greatly enable the development of concise syntheses of complex small molecules. Herein, we report the computational analysis of the energetic favorability of a key bio-inspired transformation, which we use to inform our synthetic strategy. This approach was applied to synthesize two constituents of the historically challenging indole diterpenoid class, resulting in a concise route to (–)-paspaline A in 9 steps from commercially available materials and the first pathway to and structural confirmation of emindole PB in 13 steps. This work highlights how traditional retrosynthetic design can be augmented with quantum chemical calculations to reveal energetically feasible synthetic disconnections, minimizing time-consuming and expensive empirical evaluation.

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