- Palladium-Catalyzed Hydroxycarbonylation of Aryl and Vinyl Halides or Triflates by Acetic Anhydride and Formate Anions ?
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(Equation presented) The palladium-catalyzed reaction of aryl and vinyl halides or triflates in the presence of acetic anhydride and lithium formate as a condensed source of carbon monoxide provides an efficient simple route to the synthesis of the corresponding carboxylic acids. The reaction proceeds very smoothly under mild conditions and tolerates a wide range of functional groups, including ether, ketone, ester, and nitro groups. The presence of ortho substituents does not hamper the reaction. Labeled carbonyl products can be easily prepared by using H13COONa.
- Cacchi, Sandro,Fabrizi, Giancarlo,Goggiamani, Antonella
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- Meso-13C-labeled porphyrins for studies of ground-state hole transfer in multiporphyrin arrays
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(Chemical Equation Presented) Understanding electronic communication among interacting chromophores provides the foundation for a variety of applications. The ground-state electronic communication in diphenylethyne-linked zinc-porphyrin dyads has been investigated by a novel molecular design strategy that entails introduction of a 13C-atom (*) at specific sites of the porphyrins where there is substantial electron density in the relevant frontier (highest occupied) molecular orbital. The site of 13C substitution is at a meso-position, either the site of attachment of the linker (proximal, "P") or the site trans to the linker (distal, "D"). The substituents (R) at the non-linking meso-positions are mesityl, tridec-7-yl ("swallowtail"), or p-tolyl groups. Altogether five isotopically labeled porphyrin dyads have been prepared. The hole/electron-transfer properties of one-electron oxidized dyads have been examined by electron paramagnetic resonance (EPR) spectroscopy. The introduction of the meso-13C label provides a "clock" (via the hyperfine interactions) that allows investigation of a time scale for hole transfer that is 3-4 times shorter than that provided by the natural abundance 14N nuclei of the pyrrole nitrogen atoms. The EPR studies indicate that the hole transfer, which has been previously shown to be fast on the time scale of the 14N hyperfine clock (~220 ns), remains fast on the time scale of the 13C hyperfine clock (~50 ns).
- Thamyongkit, Patchanita,Muresan, Ana Z.,Diers, James R.,Holten, Dewey,Bocian, David F.,Lindsey, Jonathan S.
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p. 5207 - 5217
(2008/02/08)
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- Structural isomers of aryl-substituted η3-propargyl complexes: η2-1-metalla(methylene)cyclopropene and η3-benzyl complexes
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Hydride abstraction from C5Me5(CO)2Re (η2-PhC≡CCH2Ph) (1) gave a 3:1 mixture of η3-propargyl complex C5Me5(CO)2Re(η3- PhCH-C≡CPh)][BF4
- Casey, Charles P.,Boller, Timothy M.,Kraft, Stefan,Guzei, Ilia A.
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p. 13215 - 13221
(2007/10/03)
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- Dynamics for reaction of an ion pair in aqueous solution: reactivity of carboxylate anions in bimolecular carbocation-nucleophile addition and unimolecular ion pair collapse.
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[reaction: see text]. The sum of the rate constants for solvolysis and 18O-scrambling of 4-MeC6H4(13)CH(Me)18OC(O)C6F5 in 50/50 (v/v) trifluoroethanol/water, k(solv) + k(iso) = 1.22 x 10(-5) s(-1), is larger than k(solv) = 1.06 x 10(-5) s(-1) for solvolys
- Tsuji,Mori,Richard,Amyes,Fujio,Tsuno
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p. 1237 - 1240
(2007/10/03)
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- Thermal isomerization of benzocyclobutene
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Thermolysis of benzocyclobutene 13CH2, 99percent gives styrene labeled in the β (48percent), ortho (30percent), α (14percent), meta (4percent), and para (4percent) positions.The major labels (β and ortho) are consistent with a mechanism involving interconversions of the isomeric tolylmethylenes and the methylcycloheptatrienes.This mechanism also involves interconversion of o-tolylmethylene with o-xylylene and p-tolylmethylene with p-xylylene.A minor mechanism produces 25percent of styrene.This mechanism involves cleavage of the aryl carbon to the methylene carbon bond in benzocyclobutene followed by hydrogen transfer to produce styrene.Thermolysis of p-xylylene produced from paracyclophane gives styrene (55percent), p-xylene (31percent), benzocyclobutene (4percent), benzene (4percent), and toluene (3percent).Thermolysis of metacyclophane gives styrene (18percent), p-xylene (25percent), m-xylene (3percent), benzocyclobutene (1percent), benzene (7percent), and toluene (22percent).
- Chapman, Orville L.,Tsou, Uh-Po Eric,Johnson, Jeffery W.
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p. 553 - 559
(2007/10/02)
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