The Trajectory of the (η5-Cyclopentadienyl)cobalt-Mediated Cycloisomerization of Ene-Yne-Ene Type Allyl Propargylic Ethers to Furans: A DFT Appraisal

Synthesis ◽  
2021 ◽  
Author(s):  
Jonathan J Wong ◽  
Xiangyang Chen ◽  
Kendall N. Houk ◽  
Peter Vollhardt
Keyword(s):  
Double Bond ◽  
Oxidative Coupling ◽  
Triple Bond ◽  
Furan Ring ◽  
Reductive Elimination ◽  
Dft Methods ◽  
Structural Details ◽  
Hydride Elimination ◽  
Cis And Trans

The mechanisms by which the complexes CpCoL2 (Cp = C5H5; L = CO or CH2=CH2) mediate the cycloisomerizations of α,,-enynenes containing allylic ether linkages is probed by DFT methods. The outcomes corroborate experimental results and provide energetic and structural details of the trajectories leading to 3-(oxacyclopentyl or cycloalkyl)furans via the intermediacy of isolable CpCo-η4-dienes. They comprise initial stereoselective complexation of one of the double bonds and the triple bond, rate determining oxidative coupling to a triplet 16e cobalta-2-cyclopentene, and terminal double bond docking, followed by stereocontrolled insertion to assemble intermediate cis- and trans-fused triplet cobalta-4-cycloheptenes. A common indicator of the energetic facility of the latter is the extent of parallel alignment of alkene moiety and its target Co-Cα bond. The cobalta-4-cycloheptenes transform further by β-hydride elimination-reductive elimination to furnish CpCo-η4-dienes, sufficiently kinetically protected to allow for their experimental observation. The cascade continues through cobalt-mediated hydride shifts and dissociation of the aromatic furan ring. The findings in silico with respect to the stereo-, regio-, and chemoselectivity are in consonance with those obtained in vitro.

Stoichiometric and Catalytic (η 5-Cyclopentadienyl)cobalt-Mediated Cycloisomerizations of Ene-Yne-Ene Type Allyl Propargyl Ethers

Synthesis ◽  
2019 ◽  
Vol 52 (03) ◽  
pp. 399-416
Author(s):  
Chu-An Chang ◽  
Stefan Gürtzgen ◽  
Erik P. Johnson ◽  
K. Peter C. Vollhardt
Keyword(s):  
Double Bond ◽  
Oxidative Coupling ◽  
Triple Bond ◽  
Furan Ring ◽  
Reductive Elimination ◽  
Potential Utility ◽  
Deuterium Labeling ◽  
Terminal Double Bond ◽  
Hydride Elimination ◽  
Diene Complex

The complexes CpCoL2 (Cp = C5H5; L = CO or CH2=CH2) mediate the cycloisomerizations of α,δ,ω-enynenes containing allylic ether linkages to 3-(oxacyclopentyl or cycloalkyl)furans via the intermediacy of isolable CpCo-η 4-dienes. A suggested mechanism comprises initial complexation of the triple bond and one of the double bonds, then oxidative coupling to a cobalt-2-cyclopentene, terminal double bond insertion to assemble a cobalta-4-cycloheptene, β-hydride elimination, and reductive elimination to furnish a CpCo-η 4-diene. When possible, the cascade continues through cobalt-mediated hydride shifts and dissociation of the aromatic furan ring. The outcome of a deuterium labeling experiment supports this hypothesis. The reaction exhibits variable stereoselectivity with a preference for the trans-product (or, when arrested, its syn-Me CpCo-η 4-diene precursor), but is completely regioselective in cases in which the two alkyne substituents are differentiated electronically by the presence or absence of an embedded oxygen. Regioselectivity is also attained by steric discrimination or blocking one of the two possible β-hydride elimination pathways. When furan formation is obviated by such regiocontrol, the sequence terminates in a stable CpCo-η 4-diene complex. The conversion of the cyclohexane-fused substrate methylidene-2-[5-(2-propenyloxy)-3-pentynyl]cyclohexane into mainly 1-[(1R*,3aS*,7aS*)-7a-methyloctahydroinden-1-yl]-1-ethanone demonstrates the potential utility of the method in complex synthesis.

Ni(COD)(DMFU): A Heteroleptic 16-Electron Precatalyst for 1,2-Diarylation of Alkenes

Synlett ◽  
2021 ◽  
Author(s):  
Nana Kim ◽  
Van T. Tran ◽  
Omar Apolinar ◽  
Steven Wisniewski ◽  
Martin Eastgate ◽  
...  
Keyword(s):  
Nickel Complex ◽  
Active Catalyst ◽  
Cross Coupling ◽  
Reductive Elimination ◽  
Coupling Reactions ◽  
Beneficial Effects ◽  
Cross Coupling Reactions ◽  
Growing Body ◽  
Hydride Elimination

Electron-deficient olefin (EDO) ligands are known to promote a variety of nickel-catalyzed cross-coupling reactions, presumably by accelerating the reductive elimination step and preventing undesired β-hydride elimination. While there is a growing body of experimental and computational evidence elucidating the beneficial effects of EDO ligands, significant gaps remain in our understanding of the underlying coordination chemistry of the Ni–EDO species involved. In particular, most procedures rely on in situ assembly of the active catalyst, and there is a paucity of pre-ligated Ni-EDO precatalysts. Herein, we investigate the 16-electron, heteroleptic nickel complex, Ni(COD)(DMFU), and examine the performance of this complex as a precatalyst in 1,2-diarylation of alkenes.

Nature of the carbon-phosphorus double bond and the carbon-phosphorus triple bond as studied by solid-state NMR

1990 ◽  
Vol 112 (19) ◽  
pp. 6803-6809 ◽  
Author(s):  
James C. Duchamp ◽  
Marek Pakulski ◽  
Alan H. Cowley ◽  
Kurt W. Zilm
Keyword(s):  
Double Bond ◽  
Solid State ◽  
Solid State Nmr ◽  
Triple Bond

scholarly journals Depth-Related Curing Potential of Ormocer- and Dimethacrylate-Based Bulk-Fill Composites

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 6753
Author(s):  
Ramona S. Oltramare ◽  
Reto Odermatt ◽  
Phoebe Burrer ◽  
Thomas Attin ◽  
Tobias T. Tauböck
Keyword(s):  
Double Bond ◽  
Repeated Measures ◽  
In Vitro Study ◽  
High Viscosity ◽  
Degree Of Conversion ◽  
Double Bond Conversion ◽  
Nanohybrid Composite ◽  
Post Hoc ◽  
One Way Anova

The aim of this in vitro study was to investigate the degree of C=C double bond conversion of high-viscosity dimethacrylate- or ormocer-based bulk-fill composites as a function of measurement depth. Four bulk-fill composites (Tetric EvoCeram Bulk Fill, x-tra fil, SonicFill, and Bulk Ormocer) and the conventional nanohybrid composite Tetric EvoCeram were applied in standardized Class II cavities (n = 6 per group) and photoactivated for 20 s at 1350 mW/cm2. The degree of conversion of the composites was assessed using Fourier-transform infrared spectroscopy at seven measurement depths (0.15, 1, 2, 3, 4, 5, 6 mm). Data were analyzed using repeated measures ANOVA and one-way ANOVA with Bonferroni post-hoc tests (α = 0.05). The investigated bulk-fill composites showed at least 80% of their maximum degree of conversion (80% DCmax) up to a measuring depth of at least 4 mm. Tetric EvoCeram Bulk Fill and Bulk Ormocer achieved more than 80% DCmax up to a measuring depth of 5 mm, x-tra fil up to 6 mm. The conventional nanohybrid composite Tetric EvoCeram achieved more than 80% DCmax up to 3 mm. In contrast to the conventional composite, the investigated ormocer- and dimethacrylate-based bulk-fill composites can be photo-polymerized in thick layers of up to at least 4 mm with regard to their degree of C=C double bond conversion.

scholarly journals 3-Phenyl-N,N,N′,N′-tetramethyl-1-ethyne-1-carboximidamidium bromide

2012 ◽  
Vol 68 (6) ◽  
pp. o1812-o1812 ◽  
Author(s):  
Ioannis Tiritiris ◽  
Willi Kantlehner
Keyword(s):  
Double Bond ◽  
Title Compound ◽  
Triple Bond ◽  
Positive Charge ◽  
Bond Distance ◽  
Double Bond Character ◽  
Acetylenic Bond ◽  
Compound C ◽  
Bond Character

The reaction of 3,3,3-tris(dimethylamino)-1-phenylprop-1-yne with bromine in pentane yields the title compound, C13H17N2 +·Br−. The acetylenic bond distance [1.197 (2) Å] is consistent with a C[triple-bond]C triple bond. The amidinium C=N bonds [1.325 (2) and 1.330 (2) Å] have double-bond character and the positive charge is delocalized between the two dimethylamino groups.

scholarly journals SYNTHESIS, IN VITRO ANTIOXIDANT AND ANTIMICROBIAL EVALUATION OF 3-HYDROXY CHROMONE DERIVATIVES

2018 ◽  
Vol 11 (3) ◽  
pp. 259
Author(s):  
Pallavi Kamble ◽  
Sailesh Wadher
Keyword(s):  
Antioxidant Activity ◽  
Double Bond ◽  
Antifungal Activity ◽  
Phenolic Hydroxyl ◽  
Hydroxyl Group ◽  
Antibacterial And Antifungal Activity ◽  
Activity Data ◽  
Group 4 ◽  
Antibacterial And Antifungal

 Objective: The objective of the present study was to synthesize a series of 3-hydroxychromone derivatives and to evaluate its in vitro antioxidant and antimicrobial activities.Methods: 3-hydroxy chromones were synthesized using an algar flynn oyamada method which includes oxidative cyclization of 2-hydroxy chalcones in basic solution by hydrogen peroxide. 2-hydroxy chalcones were synthesized by Claisen-Schmidt condensation of substituted 2-hydroxy acetophenones with substituted aromatic aldehydes using polyethylene glycol-400 as a recyclable solvent. The synthesized compounds were evaluated for in vitro antioxidant activity by 1,1-diphenyl-2-picrylhydrazyl radical scavenging assay. In addition, these compounds were also screened for in vitro antibacterial and antifungal activity by agar cup method and Poison plate method, respectively.Results: The structures of the synthesized compounds were characterized by infrared, 1H nuclear magnetic resonance and mass spectroscopy. The antioxidant activity data revealed that all the synthesized derivatives exhibited good activity due to the presence of phenolic hydroxyl group, 4-oxo group and 2,3-double bond. Further, the activity increased with the introduction of a more phenolic hydroxyl group and adjacent methoxy group in the structure. The antimicrobial activity data showed that the compounds possess better antibacterial and antifungal activity which is attributed to the presence of phenolic hydroxyl group and 4-oxo group in the structure.Conclusions: The use of inexpensive, eco-friendly and readily available reagents, easy work-up and high purity of products makes the procedure a convenient and robust method for the synthesis of title compounds. The presence of phenolic hydroxyl group, 4-oxo group, and 2,3-double bond in the structure is responsible for their good antioxidant and antimicrobial activities.

Dimethylplatinum(IV) Complexes With Cyanide: Thermal and Photoassisted Substitution Reactions, and Characterization of Products by N.M.R.

1987 ◽  
Vol 40 (9) ◽  
pp. 1565 ◽  
Author(s):  
TG Appleton ◽  
JR Hall ◽  
MA Williams
Keyword(s):  
Ultraviolet Irradiation ◽  
Oxidative Addition ◽  
Reductive Elimination ◽  
Methyl Groups ◽  
Substitution Reactions ◽  
Aqueous Acid ◽  
Cyanide Ligands ◽  
Cis And Trans ◽  
Insoluble Precipitate

Reactions of cyanide with the dimethylplatinum (IV) complexes, [PtMe2(OH) (H20)1.5 n, [PtMe2Br2]n and fac-PtMe2Br(H2O)3+, have been studied, principally by 1H, 13C and 195Pt n.m.r. Cyanide rapidly displaces the ligands trans to the methyl groups. Subsequent reactions cis to the methyl groups occur more slowly with heating, or, for bromo complexes, on ultraviolet irradiation. These substitution reactions compete with reductive elimination of groups from the platinum(IV) compounds to produce platinum(II) products. All attempts to prepare solutions of fac-PtMe2(CN)(H2O)3+ were unsuccessful. Oxidative addition of ICN to cis-PtMe2( py )2 ( py = pyridine) gave PtMe2I(CN)( py )2, from which a solution of fac-PtMe2(CN)( MeOH )3+ in methanol could be obtained. Addition of water or aqueous acid to this solution gave a very insoluble precipitate of [PtMe2(CN)(OH)n. The cis and trans influences on Jpt -C and δC of the cyanide ligands have been evaluated.

The Preparation and Biological Activity of Lactam-Based, Non-Steroidal, Inhibitors of Human Type-1 Steroid 5α-Reductase.

1998 ◽  
Vol 51 (5) ◽  
pp. 389 ◽  
Author(s):  
Andrew D. Abell ◽  
Andrew J. Phillips ◽  
Sangeeta Budhia ◽  
Ann M. McNulty ◽  
Blake L. Neubauer
Keyword(s):  
Biological Activity ◽  
Potent Inhibitor ◽  
Beckmann Rearrangement ◽  
In Vitro Assay ◽  
Vitro Assay ◽  
Human Type ◽  
Cis And Trans

A Beckmann rearrangement of cis- and trans-fused 3,4,4a,9,10,10a-hexahydrophenanthren-1(2H)-one oximes has yielded three azepines. An in vitro assay of the azepines and (3aSR,9bSR)-6-methoxy-3-methyl-1,3,3a,4,5,9b-hexahydro-2H-benz[e]indol-2-one, prepared in four steps from naphthalene-1,6-diol, against human type-1 steroid 5α-reductase, revealed the tricyclic five-membered lactam to be a potent inhibitor (IC50 733 nM).

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