- Generation and Characterization of New Fluoro-Substituted Carbenes
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Singlet fluorocarbenes substituted with diphenylphosphanyl, phenylsulfanyl, and trimethylsilyl groups were generated upon photolysis of the corresponding tricyclo[4.3.1.0]decadiene precursors 1a-c. Diphenylphosphanyl fluoro carbene 2a was directly observed by transient UV-Vis spectroscopy. Its lifetime in several solvents ranged from 1 to 10 μs. A study of its reactivity toward methyl acrylate and tetramethylethylene along with DFT calculations did not indicate specific solvation of the carbene center. Fluorothiophenyl carbene 2b and fluorotrimethylsilyl carbene 2c were studied by their reaction with pyridine to form ylides and have lifetimes of 1 μs (cyclohexane) and 33 ns (carbon tetrachloride), respectively, at room temperature. Transient UV-Vis spectroscopy supported by DFT calculations showed that, in the case of fluorothiophenyl carbene 2b, carbene formation is in competition with the generation of the diradical intermediate formed by the cleavage of only a single C-C bond of the cyclopropane ring of the precursor.
- Buron, Christophe,Tippmann, Eric M.,Platz, Matthew S.
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Read Online
- Novel electronic salt system and method for reducing unsaturated hydrocarbon compound
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The invention discloses an electronic salt system and a method for reducing unsaturated hydrocarbon compounds by using the electronic salt system, belongs to the field of organic synthesis, and solvesthe problems such as complicated operation, harsh conditions, easy generation of complex over-reduction products of methods for reducing the unsaturated hydrocarbon compounds in the prior art. An electron salt may be synthesized by an alkali metal reagent, an ether and an alcohol, the ether can be a crown ether or a cryptand; and the method adopts the electronic salt system, the unsaturated hydrocarbon compounds is reduced by the electronic salt system in an organic solvent. The method for reducing the unsaturated hydrocarbon compounds is used for reducing the unsaturated hydrocarbon compounds.
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Paragraph 0152-0156
(2018/09/08)
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- A Practical and Chemoselective Ammonia-Free Birch Reduction
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A novel protocol for a significantly improved, practical, and chemoselective ammonia-free Birch reduction mediated by bench-stable sodium dispersions and recoverable 15-crown-5 ether is reported. A broad range of aromatic and heteroaromatic compounds is reduced with excellent yields.
- Lei, Peng,Ding, Yuxuan,Zhang, Xiaohe,Adijiang, Adila,Li, Hengzhao,Ling, Yun,An, Jie
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supporting information
p. 3439 - 3442
(2018/06/26)
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- Generation and characterization of phenylsulfanylcarbene
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A photosensitive precursor (1) to phenylsulfanylcarbene 2 has been synthesized. Laser flash photolysis (308 nm) of 1 and chemical trapping studies of 2 are reported.
- Condon, Shannon E.,Buron, Christophe,Tippmann, Eric M.,Tinner, Courtney,Platz, Matthew S.
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p. 815 - 818
(2007/10/03)
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- A photoprecursor for difluorocarbene
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4,4-Difluoropyrazolidine-3,5-dione was synthesized as a precursor for the corresponding pyrazolinedione, envisioned as a photochemical source of difluorocarbene. However, this azo compound proved to be far too unstable. In contrast, 10,10-difluorobicyclo[4.3.1]deca-1,3,5-triene, readily synthesized from indane, was found to be a practical source of difluorocarbene for photochemical as well as thermal cyclopropanation reactions.
- He, Yigang,Lemal, David M.
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- The Barrier to Rotation about the Double Bond in Methylenecyclopropane
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Activation parameters have been determined in the gas phase for the geometrical isomenzation of the double bonds in two phenyl-substituted methylenecyclopropanes (2 and 8). Comparison with the analogous values for three sterically non-restricted styrene derivatives (15, 16 and 17) shows that the enthalpies of activation for the methylenecyclopropanes are lower by 3.7 kcal mol-1. This value, which is an upper limit to the amount of strain energy released by pyramidalization of the ring carbon atom in the orthogonal diradical transition state when undergoing geometrical isomerization, is considerably smaller than the value of 12-14 kcal mol-1 by which the strain energy of methylenecyclopropane is larger relative to that of cyclopropane. Our kinetics experiments thus show that the angle strain, associated with incorporating a trigonal carbon atom into the three-membered ring, is not responsible for the majority of the additional strain energy of methylenecyclopropane, relative to that of cyclopropane.
- Roth, Wolfgang R.,Quast, Michael
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p. 763 - 768
(2007/10/03)
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- Transformations Of The Bicyclonon-3-enyl Carbocation With The Charge At The C7 Atom
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7-Methyl-cis-bicyclonon-3-en-7-ol and the tosylate of cis-bicyclonon-3-en-7-ol were synthesized.It was found that the bicyclonon-3-ene carbonium cation formed intermediately during dehydration of the alcohol and during solvolysis of the tosylate does not undergo transannular cyclization.It is stabilized with the ejection of a proton, leading to bicyclononadienes.
- Nigmatova, V. B.,Zaitsev, Yu. V.,Anfilogova, S. N.,Pekhk, T. I.,Belikova, N. A.
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p. 727 - 732
(2007/10/02)
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- Equilibrium between homocub-1(9)-ene and homocub-9-ylidene
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A combination of chemical trapping and laser flash photolysis experiments is used to demonstrate that homocub-9-ylidene and homocub-1(9)-ene are in equilibrium. The equilibrium constant can be shown to be close to unity at +20°C (0.23 ≤ K ≤ 4).
- Chen, Ning,Jones Jr., Maitland,White, Walter R.,Platz, Matthew S.
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p. 4981 - 4992
(2007/10/02)
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- Deamination Reactions, 52. - Cyclopropanediazonium Ions Derived form Propellanes
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Tricyclo1,6>dec-3-en-10-amines (16, 17) and their saturated analogs (18, 19) were prepared by a multistep sequence, starting from ethyl 2-oxo-cyclopentanecarboxylate (8).The intermediate tricyclo1,6>dec-3-ene-10-carboxylic acids (14) were separated and configurationally assigned by iodolactonization of the syn isomer.Nitrous acid deaminations of the amines 16 - 19 were preformed in aqueous lithium bromide solutions.Thus, the intervening carbocations were trapped to give stable tricyclic bromides 23 - 26 as the major products.Predominant retention of the configuration was observed with all substrates although the syn-amine 17 deviated significantly from its anti isomer 16 and from the higher homologs.Charge delocalization in the tricyclic cation 31 appears to be enhanced relative to the bicyclohex-3-yl cation (3). - Keywords: Diazonium Ions/ Nucleophilic displacement/ Propellanes/ Tricyclo1,6>dec-10-yl derivatives
- Kirmse, Wolfgang,Hellwig, Georg
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p. 393 - 396
(2007/10/02)
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- Reaction of Photochemically Generated Dibromocarbene with 1,2-Dimethylenecycloalkanes. 1,4 Addition Is Real
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Photochemically or thermally generated dibromocarbene adds to a variety of 1,2-dimethylenecycloalkanes and to norborndiene to give 1,2 and 1,4 addition products.The ratios of the products of the two addition types match those found from dibromocarbene generated from bromoform.Dibromocarbene is capable of 1,4 addition.
- Le, Nguyet Anh,Jones, Maitland,Bickelhaupt, Friedrich,Wolf, Willem H. de
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p. 8491 - 8493
(2007/10/02)
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