Oxidative Decarboxylation of Podocarpic Acid Derivatives

1998 ◽  
Vol 51 (8) ◽  
pp. 653 ◽  
Author(s):  
Richard C. Cambie ◽  
Perry K. Davy ◽  
Lorna H. Mitchell ◽  
Clifton E. F. Rickard ◽  
Peter S. Rutledge
Keyword(s):  
Nitro Group ◽  
Relative Stability ◽  
High Yield ◽  
Oxidative Decarboxylation ◽  
Chain Reaction ◽  
Radical Chain ◽  
X Ray ◽  
X Ray Crystallography ◽  
Radical Chain Reaction

The radical decarboxylation–sulfoxide cycloelimination of 2′-pyridylthio esters formed from a series of podocarpic acid derivatives gives Δ4(18) -alkenes in high yield. An exception is the 13-nitro acid (2) which affords a thiohydroxamic ester (28), the relative stability of which is attributed to inhibition of the radical chain reaction by the nitro group. The stereochemistry of the pyridyl sulfide (18) has been confirmed by X-ray crystallography.

Übergangsmetallkomplexe mit Schwefelliganden, LXXV / Transition Metal Complexes with Sulfur Ligands, LXXV

1991 ◽  
Vol 46 (12) ◽  
pp. 1593-1600 ◽  
Author(s):  
Dieter Sellmann ◽  
Stefan Fünfgelder ◽  
Falk Knoch
Keyword(s):  
Reaction Mechanism ◽  
Transition Metal Complexes ◽  
Coordination Geometry ◽  
Chain Reaction ◽  
Radical Chain ◽  
X Ray ◽  
Square Planar ◽  
Product Forms ◽  
Radical Chain Reaction ◽  
Template Reaction

[Ni(′NHS′4)]2 (′NHS′42- = 2,2′-bis(2-mercaptophenylthio)diethylamine(2-)) was synthesized from Ni(ac)2 and Na2—′NHS′4 and characterized by X-ray structure analysis. In the solid state [Ni(′NHS′4)]2 contains two pseudooctahedral [Ni(′NHS′4)] fragments bridged via thiolate donors, in DMF solution at 110 °C it dissociates into mononuclear entities. The product of the template reaction between [Ni(′S′2)2]2- (′S′22- = 1,2-benzenedithiolate) and (BrC2H4)2NH was shown to contain an as yet unidentified by-product in addition to [Ni(′NHS′4)]2. Pure [Ni(′NHS′4)]2 does not react with pyridine, but the template product forms [Ni(Py)2(′S′2)] which has a square planar coordination geometry with the pyridine rings perpendicular to the NiS2N, plane.Investigation of the template formation of [Ni(′NHS′4)]2 provided evidence that the reaction of [Ni(′S′2)2]2- with (BrC2H4)2NH involves radicals, suggesting a radical chain reaction mechanism.

scholarly journals Crystal Structure and the Radiation-Induced Free-Radical Chain Reaction of 2-Deoxy-β-D-erythro-pentopyranose in the Solid State

1981 ◽  
Vol 36 (6) ◽  
pp. 726-731 ◽  
Author(s):  
Man Nien Schuchmann ◽  
Clemens von Sonntag ◽  
Yi-Hung Tsay ◽  
Carl Krüger
Keyword(s):  
Crystal Structure ◽  
Strong Temperature Dependence ◽  
Chain Reaction ◽  
Radical Chain ◽  
Interatomic Distances ◽  
X Ray ◽  
Reaction Proceeds ◽  
Radiation Induced ◽  
Free Radical Chain Reaction ◽  
Radical Chain Reaction

Abstract The crystal structure of 2-deoxy-β-D-enrythro-pentopyranose (1) was reexamined by X-ray crystallographic studies. In crystalline 1, a radiation-induced chain reaction occurs with the only product being, 2,5-dideoxy-D-enrythro-pentonic acid (4). In the chain propagating step leading to 4, an H atom is transferred over a distance of ≤ 3.3 Å as taken from interatomic distances in the unperturbed crystal. The crystal structure clearly indicates the direction by which the chain reaction proceeds through the crystal. The strong temperature dependence of G(4) is discussed in terms of temperature effects on chain initiation, propagation and termination rates.

Catalyst- and Silane- Controlled Enantioselective Hydrofunctionalization of Alkenes by Cobalt-Catalyzed Hydrogen Atom Transfer and Radical-Polar Crossover

2020 ◽  
Author(s):  
Kousuke Ebisawa ◽  
Kana Izumi ◽  
Yuka Ooka ◽  
Hiroaki Kato ◽  
Sayori Kanazawa ◽  
...  
Keyword(s):  
Hydrogen Atom ◽  
Absolute Configuration ◽  
Kinetic Resolution ◽  
Hydrogen Atom Transfer ◽  
Biologically Active ◽  
Atom Transfer ◽  
High Concentration ◽  
Chain Reaction ◽  
Radical Chain ◽  
Radical Chain Reaction

Catalytic enantioselective synthesis of tetrahydrofurans, which are found in the structures of many biologically active natural products, via a transition-metal catalyzed-hydrogen atom transfer (TM-HAT) and radical-polar crossover (RPC) mechanism is described herein. Hydroalkoxylation of non-conjugated alkenes proceeded efficiently with excellent enantioselectivity (up to 94% ee) using a suitable chiral cobalt catalyst, <i>N</i>-fluoro-2,4,6-collidinium tetrafluoroborate, and diethylsilane. Surprisingly, absolute configuration of the product was highly dependent on the steric hindrance of the silane. Slow addition of the silane, the dioxygen effect in the solvent, thermal dependency, and DFT calculation results supported the unprecedented scenario of two competing selective mechanisms. For the less-hindered diethylsilane, a high concentration of diffused carbon-centered radicals invoked diastereoenrichment of an alkylcobalt(III) intermediate by a radical chain reaction, which eventually determined the absolute configuration of the product. On the other hand, a more hindered silane resulted in less opportunity for radical chain reaction, instead facilitating enantioselective kinetic resolution during the late-stage nucleophilic displacement of the alkylcobalt(IV) intermediate.

The Pyrolytic Rearrangement of 1-Alkynoyl-3-methylpyrazoles: Synthesis of Pyrazolo[1,5-a]pyridin-5-ols and Related Compounds

1994 ◽  
Vol 47 (6) ◽  
pp. 991 ◽  
Author(s):  
RFC Brown ◽  
FW Eastwood ◽  
GD Fallon ◽  
SC Lee ◽  
RP Mcgeary
Keyword(s):  
Carbon Chain ◽  
Ring Structure ◽  
High Yield ◽  
Methyl Group ◽  
X Ray ◽  
X Ray Crystallography ◽  
Flash Vacuum Pyrolysis ◽  
Vacuum Pyrolysis ◽  
Fused Ring ◽  
Related Compounds

Flash vacuum pyrolysis of 1-(alkyn-2′-oyl)-3-methylpyrazoles at 650°/0.03 mm forms pyrazolo[1,5-a]pyridin-5-ols, often in high yield, which may bear substituents at C2, C3 or C7. In the absence of a 3-methyl group in the precursor, N-ethynylpyrazoles are formed in low yield. The formation of both types of product is interpreted as involving 3-(N-pyrazolyl)propadienones formed by N1 → N2 migration of the N-alkynoyl group with inversion of the three-carbon chain. The fused-ring structure of 2-methylpyrazolo[1,5-a]pyridin-5-ol (25) was established by X-ray crystallography of the O-benzoyl derivative (27).

An Oxidative Decarboxylation of 7-Oxopodocarpic Acid Derivatives

1990 ◽  
Vol 43 (5) ◽  
pp. 883 ◽  
Author(s):  
RC Cambie ◽  
HM Craw ◽  
CEF Rickard ◽  
JD Robertson ◽  
PS Rutledge ◽  
...  
Keyword(s):  
Optically Active ◽  
Oxidative Decarboxylation ◽  
X Ray ◽  
X Ray Crystallography

Treatment of the 7-oxopodocarpic acid derivatives (1) and (3) with 2,3-dichloro-5,6-dicyanobenzoquinone affords the conjugated dienones (5) and (6) directly. The latter compounds have potential as optically active relays for the synthesis of 3-oxygenated diterpenoids . The stereochemistry of an epoxide (7) formed from the dienone (5) has been confirmed by X-ray crystallography.

The reaction of thionitrites with barton esters: a convenient free radical chain reaction for decarboxylative nitrosation

Tetrahedron ◽  
1999 ◽  
Vol 55 (12) ◽  
pp. 3573-3584 ◽  
Author(s):  
Pierre Girard ◽  
Nadine Guillot ◽  
William B. Motherwell ◽  
Robyn S. Hay-Motherwell ◽  
Pierre Potier
Keyword(s):  
Free Radical ◽  
Chain Reaction ◽  
Radical Chain ◽  
Free Radical Chain Reaction ◽  
Radical Chain Reaction

Crystal and molecular structure of trans-[RhCl(CO)(PtBu2Ph)2]

2018 ◽  
Vol 73 (12) ◽  
pp. 1029-1032
Author(s):  
Peter Mayer ◽  
Hans-Christian Böttcher
Keyword(s):  
Molecular Structure ◽  
Ir Spectroscopy ◽  
Crystal And Molecular Structure ◽  
Title Complex ◽  
High Yield ◽  
X Ray ◽  
Carbonyl Ligands ◽  
Pale Yellow ◽  
X Ray Crystallography ◽  
Type Complex

AbstractTreatment of THF solutions containing the rhodium(II) complex trans-[RhCl2(PtBu2Ph)2] (1) with [Fe2(CO)9] in the same solvent resulted in the formation of the Vaska-type complex trans-[RhCl(CO)(PtBu2Ph)2] (2) in high yield. The title complex 2 was obtained as pale yellow crystals, characterized by NMR and IR spectroscopy, as well as by microanalyses. Additionally, the molecular structure of 2 has been established by X-ray crystallography. As often reported for similar constituted compounds, the chlorido and carbonyl ligands in crystals of 2 are strongly disordered.

Radical Chain Reaction of Alkene Molecule on H-terminated Si(100)-2×1 Surface

2008 ◽  
Vol 24 (01) ◽  
pp. 8-12
Author(s):  
YAN Hui ◽  
◽  
◽  
YUAN Shi-Ling ◽  
LIU Cheng-Bu
Keyword(s):  
Chain Reaction ◽  
Radical Chain ◽  
Radical Chain Reaction
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