The Experts below are selected from a list of 1056 Experts worldwide ranked by ideXlab platform
Andreas Greiner - One of the best experts on this subject based on the ideXlab platform.
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synthesis and properties of ω phenylalkyl substituted poly p xylylene s prepared by base induced 1 6 Dehydrohalogenation
Macromolecular Chemistry and Physics, 1999Co-Authors: Oliver Schafer, Friedel Brinkspalink, Bernd M Smarsly, C Schmidt, Joachim H Wendorff, Christian Witt, Thomas Kissel, Andreas GreinerAbstract:Reaction parameters were optimized for the synthesis of high molecular weight ω-phenylalkyl-substituted derivatives of poly(p-xylylene) (PPX) by base-induced 1,6-Dehydrohalogenation of corresponding 4-halogenomethyltoluenes. Glass transition temperatures decreased systematically with increasing alkyl spacer of the lateral substituent. The highest elongation at break was observed for the 4-phenylbutyl-substituted PPX. Level I tests on the biocompatibility of 4-phenylbutyl-substituted PPX indicated low toxicity.
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synthesis of poly p xylylene s by base induced 1 6 Dehydrohalogenation control of the degree of polymerization
Macromolecular Rapid Communications, 1999Co-Authors: Oliver Schafer, Friedel Brinkspalink, Andreas GreinerAbstract:Phenylethyl-substituted poly(p-xylylene) (PEPPX) was prepared by base-induced 1,6-Dehydrohalogenation of the corresponding 4-chloromethyltoluene. Very high degrees of polymerization of about 3150 were obtained already at low conversions. Several standard retarders for radical polymerizations failed to limit the degree of polymerization significantly. However, best control was accomplished by the addition of dibenzoyl peroxide. The degree of polymerization of PEPPX was depressed to about 110 by addition of 10–15 mol-% of dibenzoyl peroxide.
Anthony C. Willis - One of the best experts on this subject based on the ideXlab platform.
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mechanistic studies on the base promoted conversion of alkoxy substituted ring fused gem dihalocyclopropanes into furans evidence for a process involving electrocyclic ring closure of a carbonyl ylide intermediate
Journal of Organic Chemistry, 2018Co-Authors: Phillip P Sharp, Martin G Banwell, Jiri Mikusek, Elizabeth H. Krenske, Michelle L. Coote, Jas S. Ward, Anthony C. WillisAbstract:The mechanism associated with the base-promoted conversion of alkoxy-substituted and ring-fused gem-dihalocyclopropanes such as 40 into annulated furans has been explored. Treatment of compound 40 with potassium tert-butoxide affords a mixture of furans 23/27 and 41, an outcome that suggests the intermediacy of the slowly interconverting carbonyl ylides 42 and 43 that undergo rapid [1,5]-electrocyclizations and subsequent Dehydrohalogenation to afford the observed products. This proposal is supported by ab initio MO and DFT calculations that also suggest a vinylcarbene insertion pathway is less likely to be operative.
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Mechanistic Studies on the Base-Promoted Conversion of Alkoxy-Substituted, Ring-Fused gem-Dihalocyclopropanes into Furans: Evidence for a Process Involving Electrocyclic Ring Closure of a Carbonyl Ylide Intermediate
2018Co-Authors: Phillip P. Sharp, Martin G Banwell, Jiri Mikusek, Elizabeth H. Krenske, Michelle L. Coote, Jas S. Ward, Anthony C. WillisAbstract:The mechanism associated with the base-promoted conversion of alkoxy-substituted and ring-fused gem-dihalocyclopropanes such as 40 into annulated furans has been explored. Treatment of compound 40 with potassium tert-butoxide affords a mixture of furans 23/27 and 41, an outcome that suggests the intermediacy of the slowly interconverting carbonyl ylides 42 and 43 that undergo rapid [1,5]-electrocyclizations and subsequent Dehydrohalogenation to afford the observed products. This proposal is supported by ab initio MO and DFT calculations that also suggest a vinylcarbene insertion pathway is less likely to be operative
Robert G Bergman - One of the best experts on this subject based on the ideXlab platform.
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evidence for the intervention of different c h activating intermediates in the irradiation of η5 c5me5 pme3 irh2 and the reaction of η5 c5me5 pme3 ir h cl with strong base detection and spectroscopic characterization of η5 c5me5 pme3 ir li cl an intermediate in the Dehydrohalogenation reaction
Journal of the American Chemical Society, 2001Co-Authors: Thomas H Peterson, And Jeffery T Golden, Robert G BergmanAbstract:Reaction of (η5-C5Me5)(PMe3)Ir(H)(X) (X = Cl, Br) with tert-butyllithium in hydrocarbon solvent results in Dehydrohalogenation of the iridium center and subsequent C−H bond activation of solvent to give (η5-C5Me5)(PMe3)Ir(R)(H) (R = Ph, cyclohexyl, cyclooctyl). Low-temperature 1H, 31P, and 7Li NMR studies indicate that the Dehydrohalogenation reaction occurs via the formation of the intermediate (η5-C5Me5)(PMe3)Ir(Li)(X). Competition experiments involving C−H bond activation in benzene−cyclohexane−cyclooctane mixtures have allowed for the determination of a relative intermolecular selectivity scale for these substrates. The selectivities (reported on a per hydrogen basis) for benzene, cyclooctane, and cyclohexane C−H bond activation were found to be 4.98:0.74:1, respectively, and are significantly different from those obtained via photoinduced dihydrogen elimination from (η5-C5Me5)(PMe3)IrH2. Further, when Bronsted bases other than tert-butyllithium were employed, the intermolecular selectivities in the b...
Kenneth G Caulton - One of the best experts on this subject based on the ideXlab platform.
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deprotonation chloride abstraction and Dehydrohalogenation as synthetic routes to bis pyrazolate pyridyl iron ii complexes
European Journal of Inorganic Chemistry, 2017Co-Authors: Brian J Cook, Alexander V Polezhaev, Chunhsing Chen, Maren Pink, Kenneth G CaultonAbstract:The process of removal of H+ and of Cl-, Dehydrohalogenation, from (H₂L)FeCl₂ is investigated systematically, to understand the reactivity of the implied transient LFe(II). Reaction of (H₂L)FeCl₂ with 2 equivalents of LiN(SiMe₃)₂ yields LiClFe₂L₂, as its dimer with every iron 5-coordinate in an FeN₄Cl environment. To avoid Li+ cation derived from base, reaction of Na₂L with FeCl₂ gives a product Na₂[NaFe(HL)(L)]₂(LFeO) from addition of water, which reveals Na/pyrazolate Nβ interactions and a five coordinate oxo group in the OFe₃Na₂ core. Dehydrohalogenation in the presence of Ph₂PC₂H₄PPh₂ gives diamagnetic [LFe(κ²-dppe)]₂(μ-dppe) and LFe(κ²-dppe)(κ¹-dppe). Dehydrohalogenation in the presence of tBuNC gives diamagnetic LFe(CNtBu)₃. This is selectively methylated at both pyrazolate β-N to give LMeFe(tBuNC)₃²+ which is reduced with KC₈ to diamagnetic LMeFe(tBuNC)². Structure determination of these and IR data on isonitrile bands, show L²- to be a stronger donor than LMe. First installing triflate (to avoid the more persistent Cl-) facilitates access to LFe(Lewis base)₃²+ complexes, but this cation shows relatively weak binding of CO to LFeII, which implicates weak π basicity of that d6 species. Production of bis-pincer complexes (H₂L)₂Fe²+ and (LMe)₂Fe²+ in the presence of abundant Lewis base in polar medium is demonstrated, which illustrates a pincer ligand redistribution challenge to be kept in mind when trying to maintain a 1:1 Fe:pincer ratio, for highest reactivity.
Faiz Ahmed Khan - One of the best experts on this subject based on the ideXlab platform.
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an unusual formation of diarylmethane scaffolds from 4 halomethyl cyclohex 2 enone derivatives
ChemInform, 2015Co-Authors: Kaki Raveendra Babu, Faiz Ahmed KhanAbstract:This unusual dimerization of substrates (I) proceeds via a Dehydrohalogenation/1,6-conjugate addition/aromatization sequence.
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an unusual formation of diarylmethane scaffolds from 4 halomethyl cyclohex 2 enone derivatives
Tetrahedron Letters, 2015Co-Authors: Kaki Raveendra Babu, Faiz Ahmed KhanAbstract:A facile and efficient base promoted one-pot dimerization of halo cyclohexene derivatives leading to a de novo synthesis of biologically important diarylmethane and diarylmethanone derivatives is reported. A plausible mechanism for the unexpected formation of the title compounds involves Dehydrohalogenation, 1,6-conjugate addition, subsequent aromatization through C–C bond cleavage and Dehydrohalogenation.