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Catalytic Asymmetric Synthesis of Cycloalkanes via Cascade Reactions of Nitroalkenes
Published in Irishi N. N. Namboothiri, Meeta Bhati, Madhu Ganesh, Basavaprabhu Hosamani, Thekke V. Baiju, Shimi Manchery, Kalisankar Bera, Catalytic Asymmetric Reactions of Conjugated Nitroalkenes, 2020
Irishi N. N. Namboothiri, Meeta Bhati, Madhu Ganesh, Basavaprabhu Hosamani, Thekke V. Baiju, Shimi Manchery, Kalisankar Bera
The Enders group described a one-pot Michael addition/Conia-ene reaction of nitroalkenes 1e with 1,3-dicarbonyl compounds 34 in a sequential manner by employing a combination of organocatalyst, i.e., squaramide-based catalyst C6b and metal catalyst (indium triflate) to synthesize highly functionalized methylene indanes 72 and methyl indenes 73 in good yields and high enantioselectivities (Scheme 10.25).57 The reaction is assumed to proceed through concerted fragmentation mechanism, where first, enolization of methylene indane 72 R1 = alkyl) occurs followed by the fragmentation to form methyl indene 73 with the extrusion of ketene, presumably via enolization and a concerted fragmentation, as evidenced by high resolution mass spectrometry (HRMS).
Ring-Opening Polymerization and Metathesis Polymerizations
Published in Samir H. Chikkali, Metal-Catalyzed Polymerization, 2017
Various complex polymer architectures have also been obtained using ADMET. Grubbs and coworkers have synthesized mechanically interlocked polymers such as polyrotaxanes and daisy-chain polymers via ADMET.82,83 Hyperbranched polymers are highly branched polymers that possess higher solubility and lower viscosity due to large number of end groups. These are typically synthesized in single-step reaction from ABn (n ≥ 2)-type monomers using condensation or CRP chemistry. Selectivity of the cross-coupling of electron-rich and electron-deficient olefins was used to synthesize hyperbranched polymers from an AB2 monomer containing one terminal olefin and two acrylates using ADMET catalyzed by Grubbs [Ru]-2 catalyst.84 The acrylate groups at the periphery were reacted with a pyrene derivative using cross-metathesis to modify properties of the polymer. Hyperbranched polyphosphoester with acrylate end groups was synthesized using a similar approach, and intramolecular crosslinking of endgroups was used to get polymer nanoparticles.85 Linear-dendritic polyphosphoester copolymer was synthesized using alkene-acrylate reaction in combination with ADMET and thiol-ene reaction.86
Dispersants
Published in Leslie R. Rudnick, Lubricant Additives, 2017
These anhydrides can be converted into phthalic anhydrides through dehydrogenation by using sulfur [50–52]. These compounds can then be transformed into dispersants by reacting with polyamines and polyhydric alcohols [51,52]. During the thermal reaction of polyisobutylene with maleic anhydride, that is, the ene reaction, the vinylidene double bond moves down the chain to the next carbon. Since thermal reaction requires a terminal olefin, further reaction of the new olefin with another mole of maleic anhydride will not occur if the double bond internalizes, and the reaction will stop at this stage. This is shown in Reaction 3.3 of Figure 3.6. If the new double bond is external, the reaction with another molecule of maleic anhydride is possible [45]. This is shown in Reaction 3.4.
Reactions of singlet oxygen with cholesterol: a computational study
Published in Molecular Physics, 2023
Anna M. Tsouri, David Robinson
For each of the reactions of singlet oxygen with cholesterol considered, double-bond migration is observed, consistent with the ‘ene’ reaction. Production of R-6-hydroperoxycholesterol proceeds through a one-step, concerted mechanism, with oxygen addition and removal of a hydrogen atom from a neighbouring carbon (resulting in the double-bond migration), while production of 5-hydroperoxycholesterol and S-6-hydroperoxycholesterol proceeds via a two-step reaction, with the C–O bond forming first, followed by removal of the hydrogen atom from the C–H bond, leading to the double bond migration. These same results were also seen in the gas phase calculations (see Supporting Information). Both the 5-hydroperoxycholesterol and S-6-hydroperoxycholesterol pathways have an epoxide-like intermediate (Schemes 1 and 3); these could be the starting point for production of the significant (parts-per-million) levels of 5,6-epoxides found in in human blood [12]. This intermediate may therefore react with NO2 in vivo to produce these epoxides [49].
Thiol-ene reaction based polymer dispersed liquid crystal composite films with low driving voltage and high contrast ratio
Published in Liquid Crystals, 2020
Tingjun Zhong, Richard J. Mandle, John W. Goodby, Cuihong Zhang, Lanying Zhang
The thiol-ene reaction forms an alkyl sulphide from a thiol and an alkene and has been widely employed in the preparation of both linear and cross-linked polymer networks [27,28]. The simple chemistry and highly accessible starting materials render the thiol-ene reaction a useful stratagem for preparing PDLC films. The nucleophile-initiated thiol-ene click reaction demonstrated in PDLC system has been investigated by Shi et al, whom have illustrated that with the increase of thiol functionality, the threshold voltage and saturation voltage of the thiol-ene based PDLC films increases and the off-state transmittance decreases [29,30]. Except for changing the conditions of polymerization, Shi et al. have reported a dye-doped thiol-ene based PDLC system with a low threshold voltage [31]. Without UV irradiation, they have also added nitrogen-centred catalysts such as 4-dimethylaminopyridine for fabricating thiol-ene based PDLCs [32]. Zhang et al. achieved a thiol-ene based PDLC film with superior properties of a low-driving voltage (37.2 V), a high contrast ratio (148.2), and ashort response time (14.9 ms) via the investigation of the effects of crosslinking agent/diluents/thiol on the electro-optic properties [33]. Sun et al. found a thiol-acrylate PDLC system where the polymer network and electro-optic properties were easily tunable by the introduction of thiol monomers [34] Moreover, when adding a poly-mercaptan curing agent with an appropriate concentration into a polymer dispersed cholesteric liquid crystal system, lower voltages and high contrast ratios were achieved [35,36].
Copper-assisted synthesis of five-membered O-heterocycles
Published in Inorganic and Nano-Metal Chemistry, 2020
Navjeet Kaur, Yamini Verma, Neha Ahlawat, Pooja Grewal, Pranshu Bhardwaj, Nirmala Kumari Jangid
Balme and coworkers[51–58] reported that anti-carbocupration of stabilized nucleophiles onto non-activated alkynes with Cu(I) catalyst occurred at room temperature. Dixon and coworkers[59] synthesized cyclopentenes with metal complexes and also utilized Cu(I) complexes associated with a cinchona based thiourea organocatalyst for enantioselective and room temperature version of the Conia-ene reaction of β-keto esters.[60] The carbocyclization of few nitrogen and various carbon tethered substrates occurred under mild conditions by Cu(I) based metallo-organocatalytic system.[61] The indane, cyclopentane, tetrahydrofuran, and pyrrolidine frameworks (Scheme 14) were synthesized following this protocol [62].