- Evidence of a double surface crossing between open- and closed-shell surfaces in the photodissociation of cyclopropyl iodide
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Gas-phase photodissociations of cyclopropyl iodide were conducted at 266 and 279.7 nm, and the radical products were probed by multiphoton ionization, with imaging of the resulting ions and their corresponding electrons. Solution-phase photodissociations of cyclopropyl iodide were also conducted with TEMPO-trapping of the radical dissociation products. In both gas and solution phases, allyl radical was found to be a direct product of the cyclopropyl iodide photodissociation. CASSCF calculations indicate that the allyl radical could be formed directly from photoexcited cyclopropyl iodide by way of two surface crossings between open- and closed-shell potential energy surfaces. Each surface crossing represents a point of potential bifurcation in the reaction dynamics. Thus, cyclopropyl iodide that is excited to a 1(n,σ*) state can remain on an open-shell surface and generate the cyclopropyl radical and an iodine atom or can cross to a closed-shell (ion-pair) surface. The cyclopropyl cation that results from the surface crossing can undergo barrierless ring opening to the allyl cation before crossing back to an open-shell surface to generate allyl radical and an iodine atom. In this manner, both cyclopropyl radical and allyl radical can be formed as direct products of cyclopropyl iodide photodissociation.
- Arnold, Pamela A.,Cosofret, Bogdan R.,Dylewski, Scott M.,Houston, Paul L.,Carpenter, Barry K.
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- Direct Synthesis of Heavy Grignard Reagents: Challenges, Limitations, and Derivatization
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The direct synthesis of organocalcium compounds (heavy Grignard reagents) by the reduction of organyl halides with activated calcium powder succeeded in a straightforward manner for organic bromides and iodides that are bound at sp2-hybridized carbon atoms. Extension of this strategy to alkyl halides was very limited, and only the reduction of trialkylsilylmethyl bromides and iodides with activated calcium allowed the isolation of the corresponding heavy Grignard reagents. Substitution of only one hydrogen atom of the methylene moiety by a phenyl or methyl group directed this reduction toward the Wurtz-type coupling and the formation of calcium halide and the corresponding C?C coupling product. The stability of the methylcalcium and benzylcalcium derivatives in ethereal solvents suggests an unexpected reaction behavior of the intermediate organyl halide radical anions. Quantum chemical calculations verify a dependency between the ease of preparative access to organocalcium complexes and the C?I bond lengths of the organyl iodides. The bulkiness of the trialkylsilyl group is of minor importance. Chloromethyltrimethylsilane did not react with activated calcium; however, halogen-exchange reactions allowed the isolation of [Ca(CH2SiMe3)(thf)3(μ-Cl)]2. Furthermore, the metathetical approach of reacting [Ca(CH2SiMe3)I(thf)4] with KN(SiMe3)2 and the addition of N,N,N′,N′′,N′′-pentamethyldiethylenetriamine (pmdeta) allowed the isolation of heteroleptic [CaCH2SiMe3{N(SiMe3)2}(pmdeta)]. In the reaction of this derivative with phenylsilane, the trimethylsilylmethyl group proved to be more reactive than the bis(trimethylsilyl)amido substituent.
- Koch, Alexander,Dufrois, Quentin,Wirgenings, Marino,G?rls, Helmar,Krieck, Sven,Etienne, Michel,Pohnert, Georg,Westerhausen, Matthias
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- Synthetic method and process of halogenated cyclopropane
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The invention discloses a synthetic method and process of halogenated cyclopropane. The synthesis method and process comprise the following two steps of: (1) reacting cyclopropylamine serving as a rawmaterial with halogenated metal salt in the presence of nitrosation reagents such as nitrous acid ester to obtain 1, 1-dihalogenated cyclopropane; and (2) carrying out metallization reaction on the 1, 1dihalogenated cyclopropane and an organic metal reagent, and hydrolyzing to obtain halogenated cyclopropane. The synthesis method and process have the advantages that toxic reagents causing environmental pollution are not used, the purity and yield of the obtained product are high, and the synthesis method and process are suitable for industrial production.
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Paragraph 0018
(2021/03/31)
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