Iron-Catalyzed C—H Insertions: Organometallic and Enzymatic Carbene Transfer Reactions

2018 ◽  
Author(s):  
Katharina J. Hock ◽  
Anja Knorrscheidt ◽  
Renè Hommelsheim ◽  
Junming Ho ◽  
Martin J. Weissenborn ◽  
...  
Keyword(s):  
Iron Reduction ◽  
Kinetic Isotope Effect ◽  
Heme Iron ◽  
Transfer Reactions ◽  
Deuterium Labeling ◽  
Reaction Conditions ◽  
Kinetic Isotope ◽  
Earth Abundant ◽  
First Time ◽  
Iron Based Catalysts

<p>C—H insertion reactions with organometallic and enzymatic catalysts based on earth-abundant iron complexes remain one of the major challenges in organic synthesis. In this report, we describe the development and application of these iron-based catalysts in the reaction of two different carbene precursors with <i>N-</i>heterocycles for the first time. While FeTPPCl showed excellent reactivity in the Fe(III) state with diazoacetonitrile, the highest activities of the YfeX enzyme could be achieved upon heme-iron reduction to Fe(II) with both diazoacetonitrile and ethyl diazoacetate. This highlights unexpected and subtle differences in reactivity of both iron catalysts. Deuterium labeling studies indicated a C—H insertion pathway and a marked kinetic isotope effect. This transformation features mild reaction conditions, excellent yields or turnover numbers with broad functional group tolerance, including gram-scale applications giving a unique access to functionalized <i>N</i>-heterocycles.</p>

Iron-Catalyzed C—H Insertions: Organometallic and Enzymatic Carbene Transfer Reactions

2018 ◽  
Author(s):  
Katharina J. Hock ◽  
Anja Knorrscheidt ◽  
Renè Hommelsheim ◽  
Junming Ho ◽  
Martin J. Weissenborn ◽  
...  
Keyword(s):  
Iron Reduction ◽  
Kinetic Isotope Effect ◽  
Heme Iron ◽  
Transfer Reactions ◽  
Deuterium Labeling ◽  
Reaction Conditions ◽  
Kinetic Isotope ◽  
Earth Abundant ◽  
First Time ◽  
Iron Based Catalysts

<p>C—H insertion reactions with organometallic and enzymatic catalysts based on earth-abundant iron complexes remain one of the major challenges in organic synthesis. In this report, we describe the development and application of these iron-based catalysts in the reaction of two different carbene precursors with <i>N-</i>heterocycles for the first time. While FeTPPCl showed excellent reactivity in the Fe(III) state with diazoacetonitrile, the highest activities of the YfeX enzyme could be achieved upon heme-iron reduction to Fe(II) with both diazoacetonitrile and ethyl diazoacetate. This highlights unexpected and subtle differences in reactivity of both iron catalysts. Deuterium labeling studies indicated a C—H insertion pathway and a marked kinetic isotope effect. This transformation features mild reaction conditions, excellent yields or turnover numbers with broad functional group tolerance, including gram-scale applications giving a unique access to functionalized <i>N</i>-heterocycles.</p>

scholarly journals Pressure dependence of the deuterium isotope effect in the photolysis of formaldehyde by ultraviolet light

2010 ◽  
Vol 10 (7) ◽  
pp. 3455-3462 ◽  
Author(s):  
E. J. K. Nilsson ◽  
V. F. Andersen ◽  
H. Skov ◽  
M. S. Johnson
Keyword(s):  
Isotope Effect ◽  
Pressure Dependence ◽  
Kinetic Isotope Effect ◽  
Ambient Pressure ◽  
Deuterium Isotope Effect ◽  
Kinetic Isotope ◽  
Molecular Channel ◽  
The University ◽  
First Time ◽  
Gas Pressures

Abstract. The pressure dependence of the relative photolysis rate of HCHO vs. HCDO has been investigated for the first time, using a photochemical reactor at the University of Copenhagen. The dissociation of HCHO vs. HCDO using a UVA lamp was measured at total bath gas pressures of 50, 200, 400, 600 and 1030 mbar. The products of formaldehyde photodissociation are either H2 + CO (molecular channel) or HCO + H (radical channel), and a photolysis lamp was chosen to emit light at wavelengths that greatly favor the molecular channel. The isotope effect in the dissociation, kHCHO/kHCDO, was found to depend strongly on pressure, varying from 1.1 + 0.15/−0.1 at 50 mbar to 1.75±0.10 at 1030 mbar. The results can be corrected for radical channel contribution to yield the kinetic isotope effect for the molecular channel; i.e. the KIE in the production of molecular hydrogen. This is done and the results at 1030 mbar are discussed in relation to previous studies at ambient pressure. In the atmosphere the relative importance of the two product channels changes with altitude as a result of changes in pressure and actinic flux. The study demonstrates that the δD of photochemical hydrogen produced from formaldehyde will increase substantially as pressure decreases.

Hydride transfer reactions. A kinetic study of oxidation of 10-methyl-9-phenylacridan by some π acceptors and a one-electron oxidant

1985 ◽  
Vol 63 (8) ◽  
pp. 2237-2240 ◽  
Author(s):  
Allan K. Colter ◽  
A. Gregg Parsons ◽  
Karen Foohey
Keyword(s):  
Kinetic Study ◽  
Kinetic Isotope Effect ◽  
Isotope Effects ◽  
Hydride Transfer ◽  
Transfer Reactions ◽  
Kinetics Of Oxidation ◽  
Kinetic Isotope ◽  
One Step ◽  
The One ◽  
Kinetics Of

The kinetics of oxidation of 10-methyl-9-phenylacridan (1(H)) and 9-deuterio-10-methyl-9-phenylacridan (1(D)) to 10-methyl-9-phenylacridinium ion (3) by eight oxidants have been investigated. The oxidants included the π-acceptors 1,4-benzoquinone (BQ), 7,7,8,8-tetracyanoquinodimethane (TCNQ), p-bromanil (BA), p-chloranil (CA), tetracyanoethylene (TCNE), 2,3-dicyano-1,4-benzoquinone (DCBQ) and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) in acetonitrile (AN), BQ in 50:50 (v/v) AN-water, and the one-electron oxidant tris(2,2′-bipyridyl)cobalt(III), [Formula: see text] in AN. The seven π acceptors cover a 109-fold range of reactivity from BQ to DDQ and the deuterium kinetic isotope effect varies from 11.9 (BQ in AN) to 5.8 (DDQ). For π acceptors (BQ, TCNQ, CA, TCNE, and DCBQ) previously investigated with 10-methylacridan (NMA), 1(H) is less reactive than NMA by factors ranging from 9.1 (BQ) to 1.7 × 102 (TCNE). The isotope effects and relative reactivities for the π acceptor oxidations are most simply explained by a one-step hydride transfer mechanism.

Intramolecular kinetic isotope effect in gas-phase proton-transfer reactions

1979 ◽  
Vol 101 (8) ◽  
pp. 2242-2243 ◽  
Author(s):  
Keith M. Wellman ◽  
Maria E. Victoriano ◽  
Paulo C. Isolani ◽  
Jose M. Riveros
Keyword(s):  
Proton Transfer ◽  
Gas Phase ◽  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Transfer Reactions ◽  
Kinetic Isotope ◽  
Proton Transfer Reactions

scholarly journals Iron-Catalyzed Silylation of Alcohols by Transfer Hydrosilylation with Silyl Formates

Synlett ◽  
2017 ◽  
Vol 28 (18) ◽  
pp. 2473-2477 ◽  
Author(s):  
Thibault Cantat ◽  
Timothé Godou ◽  
Clément Chauvier ◽  
Pierre Thuéry
Keyword(s):  
Transition Metal ◽  
Iron Catalyst ◽  
Metal Catalyst ◽  
Reaction Conditions ◽  
Transition Metal Catalyst ◽  
Earth Abundant ◽  
First Time

An iron catalyst is shown for the first time to promote transfer hydrosilylation with silyl formates and is utilized for the silylation of alcohols. Attractive features of this protocol include the use of an earth-abundant transition-metal catalyst, mild reaction conditions, and the release of gases as the only byproducts (H2 and CO2).

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