21889-88-3Relevant academic research and scientific papers
Solvent, counterion, and secondary deuterium kinetic isotope effects in the anionic oxy-Cope rearrangement
Gajewski, Joseph J.,Gee, Kyle R.
, p. 967 - 971 (1991)
The potassium and sodium alkoxides of 3-methyl-1,5-hexadien-3-ol follow first-order kinetics in the process of undergoing the anionic oxy-Cope rearrangement in tetrahydrofuran (THF) and dimethyl sulfoxide (DMSO). The first-order rate constant for the rearrangement of the potassium alkoxide in DMSO is ca. 1000 times faster than that in THF, as is the first-order rate constant in THF in the presence of 1 equiv or excess 18-crown-6. The rate constants in THF are independent of initial alkoxide concentration; in contrast, the first-order rate constants in DMSO are inversely proportional to the initial alkoxide concentration, and addition of potassium salts to the DMSO solution results in a retardation of rearrangement rate. Addition of 1/4 and 1/2 equiv of 18-crown-6 in THF gave first-order behavior only over the first 25% of reaction with an initial rate constant linearly related to that with 1 equiv of crown ether. Secondary deuterium kinetic isotope effects have been determined at the bond-breaking and bond-making sites in the Cope rearrangement of the potassium alkoxide in THF, in THF in the presence of 18-crown-6, and in DMSO. The isotope effects indicate a highly dissociative transition state with substantial bond breaking of the C3-C4 bond and little bond making between the allylic termini (C1 and C6). The effects of aggregation and ionic dissociation are discussed in the context of mechanistic pathways proposed for the rearrangement in THF and in DMSO.
Chemiluminescence-promoted oxidation of alkyl enol ethers by NHPI under mild conditions and in the dark
Anderson,Andia, Alexander A.,Woerpel
supporting information, (2021/02/03)
The hydroperoxidation of alkyl enol ethers using N-hydroxyphthalimide and molecular oxygen occurred in the absence of catalyst, initiator, or light. The reaction proceeds through a radical mechanism that is initiated by N-hydroxyphthalimide-promoted autoxidation of the enol ether substrate. The resulting dioxetane products decompose in a chemiluminescent reaction that allows for photochemical activation of N-hydroxyphthalimide in the absence of other light sources.
Iron-Catalyzed Synthesis of α-Dienyl Five- and Six-Membered N-Heterocycles
Gonnard, Laurine,Guérinot, Amandine,Cossy, Janine
supporting information, p. 6160 - 6167 (2017/11/15)
The iron-catalyzed synthesis of α-dienyl N-heterocycles is reported. The method is cost-effective, atom-economic, and led to a range of substituted α-dienyl heterocycles in moderate to good yields and diastereoselectivities. The α-dienyl piperidines are key synthetic intermediates as demonstrated by the preparation of a panel of α-polyenyl N-heterocycles.
Synthesis of 3D-Rich Heterocycles: Hexahydropyrazolo[1,5-A]pyridin-2(1H)-ones and Octahydro-2H-2a,2a1-diazacyclopenta[cd]inden-2-ones
Pu?avec Kirar, Eva,Drev, Miha,Mirnik, Jona,Gro?elj, Uro?,Golobi?, Amalija,Dahmann, Georg,Po?gan, Franc,?tefane, Bogdan,Svete, Jurij
, p. 8920 - 8933 (2016/10/14)
Two cyclic azomethine imines, 7-methyl- and 7-phenyl-2-oxo-Δ7-hexahydropyrazolo[1,5-A]pyridin-8-ium-1-ide, were prepared in seven steps from the respective commercially available δ-keto acids. The addition of Grignard reagents followed by N-Alkylation at position 1 afforded the 1,7,7-trisubstituted hexahydropyrazolo[1,5-A]pyridin-2(1H)-ones, whereas 1,3-dipolar cycloadditions of these dipoles to typical acetylenic and olefinic dipolarophiles gave 4a-substituted 2a,2a1-diazacyclopenta[cd]indene derivatives as the first representatives of a novel heterocyclic system. Regio- and stereoselectivity as well as the mechanism of these [3 + 2]-cycloadditions were evaluated using computational and experimental methods. The data obtained were in agreement with the polar concerted cycloaddition mechanism via the energetically favorable syn/endo-transition states.
Visible Light Photocatalysis of Carbon-Carbon σ-Bond Anaerobic Oxidation of Ketones with Water by Cobalt(II) Porphyrins
Lee, Siu Yin,Fung, Hong Sang,Feng, Shiyu,Chan, Kin Shing
supporting information, p. 2480 - 2487 (2016/08/16)
CoII(por) (por = porphyrinato dianion) reacted selectively with isopropyl ketones at the carbon (CO)-carbon (α) bond at room temperature to give high yields of CoIII(por) acyls and the corresponding oxidized carbonyl compounds in up
Is H Atom Abstraction Important in the Reaction of Cl with 1-Alkenes?
Walavalkar,Vijayakumar,Sharma,Rajakumar,Dhanya
, p. 4096 - 4107 (2016/07/06)
The relative yields of products of the reaction of Cl atoms with 1-alkenes (C4-C9) were determined to see whether H atom abstraction is an important channel and if it is to identify the preferred position of abstraction. The presence of all the possible positional isomers of long chain alkenones and alkenols among the products, along with chloroketones and chloroalcohols, confirms the occurrence of H atom abstraction. A consistent pattern of distribution of abstraction products is observed with oxidation at C4 (next to allyl) being the lowest and that at CH2 groups away from the double bond being the highest. This contradicts with the higher stability of allyl (C3) radical. For a better understanding of the relative reactivity, ab initio calculations at MP2/6-311+G (d,p) level of theory are carried out in the case of 1-heptene. The total rate coefficient, calculated using conventional transition state theory, was found to be in good agreement with the experimental value at room temperature. The preferred position of Cl atom addition is predicted to be the terminal carbon atom, which matches with the experimental observation, whereas the rate coefficients calculated for individual channels of H atom abstraction do not explain the observed pattern of products. The distribution of abstraction products except at C4 is found to be better explained by reported structure activity relationship, developed from experimental rate coefficient data. This implies the reactions to be kinetically dictated and emphasizes the importance of secondary reactions.
Transaminase Triggered Aza-Michael Approach for the Enantioselective Synthesis of Piperidine Scaffolds
Ryan, James,?iau?iulis, Mindaugas,Gomm, Andrew,Maciá, Beatriz,O’Reilly, Elaine,Caprio, Vittorio
supporting information, p. 15798 - 15800 (2016/12/22)
The expanding “toolbox” of biocatalysts opens new opportunities to redesign synthetic strategies to target molecules by incorporating a key enzymatic step into the synthesis. Herein, we describe a general biocatalytic approach for the enantioselective preparation of 2,6-disubstituted piperidines starting from easily accessible pro-chiral ketoenones. The strategy represents a new biocatalytic disconnection, which relies on an ω-TA-mediated aza-Michael reaction. Significantly, we show that the reversible enzymatic process can power the shuttling of amine functionality across a molecular framework, providing access to the desired aza-Michael products.
Catalytic asymmetric total synthesis of (S)-(-)-zearalenone, a novel lipoxygenase inhibitor
Baggelaar, Marc P.,Huang, Yange,Feringa, Ben L.,Dekker, Frank J.,Minnaard, Adriaan J.
, p. 5271 - 5274 (2013/09/02)
A catalytic asymmetric synthesis of (S)-(-)-zearalenone is reported using asymmetric allylic alkylation for the introduction of the stereocenter. (S)-(-)-Zearalenone turned out to be a novel lipoxygenase inhibitor.
Synthesis and reactivity of unsymmetrical azomethine imines formed using alkene aminocarbonylation
Gan, Wei,Moon, Patrick J.,Clavette, Christian,Das Neves, Nicolas,Markiewicz, Thomas,Toderian, Amy B.,Beauchemin, Andre M.
supporting information, p. 1890 - 1893 (2013/06/05)
Complex cyclic azomethine imines possessing a β-aminocarbonyl motif can be accessed readily from simple alkenes and hydrazones. This alkene aminocarbonylation approach allows formation of ketone-derived azomethine imines of unprecedented complexity. Since unsymmetrical hydrazones are used, two stereoisomers are formed: the reactivity of chiral derivatives is explored in both intra- and intermolecular systems.
FeCl3-catalyzed highly diastereoselective synthesis of substituted piperidines and tetrahydropyrans
Guerinot, Amandine,Serra-Muns, Anna,Gnamm, Christian,Bensoussan, Charlelie,Reymond, Sebastien,Cossy, Janine
supporting information; experimental part, p. 1808 - 1811 (2010/10/03)
The eco-friendly and highly diastereoselective synthesis of substituted cis-2,6-piperidines and cis-2,6-tetrahydropyrans is described. The key step of this method is the iron-catalyzed thermodynamic equilibration of 2-alkenyl 6-substituted piperidines and 2-alkenyl 6-substituted tetrahydropyrans allowing the isolation of enriched mixtures of the most stable cis-isomers.
