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W. C. Lineberger - One of the best experts on this subject based on the ideXlab platform.
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ultraviolet photoelectron spectroscopy of the o m and p Benzyne negative ions electron affinities and singlet triplet splittings for o m and p Benzyne
Journal of the American Chemical Society, 1998Co-Authors: Paul G. Wenthold, Robert R. Squires, W. C. LinebergerAbstract:The 351 nm photoelectron spectra of the negative ions of o-, m-, and p-Benzyne (1,2-, 1,3-, and 1,4-dehydrobenzene, respectively) and their perdeuterated isotopomers have been obtained. The o-Benzyne ions were generated by the reaction of benzene and benzene-d6 with O-, while the m- and p-Benzyne ions were prepared by the gas-phase reaction between the corresponding 3- and 4-(trimethylsilyl)phenyl anions and molecular fluorine, F2. The photoelectron spectra of the Benzyne anions each contain two features, corresponding to formation of the singlet and triplet states of the biradicals. The electron affinities of o- and p-Benzyne are found to be 0.564 ± 0.007 and 1.265 ± 0.008 eV, respectively, while the electron affinities of deuterated o- and p-Benzyne are found to be 8 and 5 meV lower, respectively. The electron affinity of m-Benzyne could not be determined from the photoelectron spectrum because the origin peak could not be assigned unequivocally. For o- and p-Benzyne, the singlet−triplet energy splittin...
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Ultraviolet Photoelectron Spectroscopy of the o-, m-, and p- Benzyne Negative Ions. Electron Affinities and Singlet−Triplet Splittings for o -, m -, and p -Benzyne
Journal of the American Chemical Society, 1998Co-Authors: Paul G. Wenthold, Robert R. Squires, W. C. LinebergerAbstract:The 351 nm photoelectron spectra of the negative ions of o-, m-, and p-Benzyne (1,2-, 1,3-, and 1,4-dehydrobenzene, respectively) and their perdeuterated isotopomers have been obtained. The o-Benzyne ions were generated by the reaction of benzene and benzene-d6 with O-, while the m- and p-Benzyne ions were prepared by the gas-phase reaction between the corresponding 3- and 4-(trimethylsilyl)phenyl anions and molecular fluorine, F2. The photoelectron spectra of the Benzyne anions each contain two features, corresponding to formation of the singlet and triplet states of the biradicals. The electron affinities of o- and p-Benzyne are found to be 0.564 ± 0.007 and 1.265 ± 0.008 eV, respectively, while the electron affinities of deuterated o- and p-Benzyne are found to be 8 and 5 meV lower, respectively. The electron affinity of m-Benzyne could not be determined from the photoelectron spectrum because the origin peak could not be assigned unequivocally. For o- and p-Benzyne, the singlet−triplet energy splittin...
Thomas R Hoye - One of the best experts on this subject based on the ideXlab platform.
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Benzyne Cascade Reactions via Benzoxetenonium Ions and Their Rearrangements to o-Quinone Methides.
Organic Letters, 2019Co-Authors: Hang Shen, Xiao Xiao, Thomas R HoyeAbstract:A new thermal isomerization of polyynes is described. Benzyne intermediates substituted by a C(RR′)OR′′ substituent adjacent to one of the Benzyne sp-hybridized carbons give rise to products in which the OR′ moiety has migrated to the proximal Benzyne carbon. This process likely proceeds via sequential formation of multiple reactive intermediates: an initial thermally generated Benzyne, a strained benzoxetenonium ion, and an o-quinone methide. As some examples demonstrate, the overall transformation can be quite efficient. The mechanism of this novel reaction is further supported by experiments and DFT calculations.
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Divergent Reactivity during the Trapping of Benzynes by Glycidol Analogs: Ring Cleavage via Pinacol-Like Rearrangements vs Oxirane Fragmentations
2019Co-Authors: Juntian Zhang, Thomas R HoyeAbstract:Hydroxy-containing cyclic ethers react with thermally generated Benzynes to produce aryl ethers. Diverse reactivity was observed. Cleavage of the cyclic ether was involved in most of the pathways. The transformations are rationalized via initial formation of oxonium ion-containing 1,3-zwitterions arising from preferential nucleophilic attack on the Benzyne by the ether oxygen. Pinacol-like rearrangements, including ring expansion, to yield aldehydes or ketones and oxirane fragmentations to generate aryl enol ethers were main competing events
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Benzyne Cascade Reactions via Benzoxetenonium Ions and Their Rearrangements to o‑Quinone Methides
2019Co-Authors: Hang Shen, Xiao Xiao, Thomas R HoyeAbstract:A new thermal isomerization of polyynes is described. Benzyne intermediates substituted by a C(RR′)OR′′ substituent adjacent to one of the Benzyne sp-hybridized carbons give rise to products in which the OR′ moiety has migrated to the proximal Benzyne carbon. This process likely proceeds via sequential formation of multiple reactive intermediates: an initial thermally generated Benzyne, a strained benzoxetenonium ion, and an o-quinone methide. As some examples demonstrate, the overall transformation can be quite efficient. The mechanism of this novel reaction is further supported by experiments and DFT calculations
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Reactions of Diaziridines with Benzynes Give N-Arylhydrazones.
Organic Letters, 2018Co-Authors: Sahil Arora, Vignesh Palani, Thomas R HoyeAbstract:Reactions of thermally generated Benzynes with diaziridines are reported. These trapping reactions follow the same pathway as reported earlier by Heine and co-workers with electron-deficient alkynes. The resulting N-arylhydrazones were obtained efficiently in a single step. The preference for the mode of addition of the nucleophilic diaziridine nitrogen atom to the more electrophilic Benzyne carbon was consistent with what is predicted on the basis of distortion analysis. The feasibility of converting the hydrazone into a Fisher-indole adduct was demonstrated.
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BF3‑Promoted, Carbene-like, C–H Insertion Reactions of Benzynes
2018Co-Authors: Hang Shen, Patrick H Willoughby, Xiao Xiao, Moriana K. Haj, Thomas R HoyeAbstract:Boron trifluoride is observed to promote a variety of C–H insertion reactions of Benzynes bearing pendant alkyl groups. Computations and various mechanistic studies indicate that BF3 engages the strained π-bond to confer carbene-like character on the adjacent, noncoordinated Benzyne carbon. This represents an unprecedented catalytic role for a non-transition metal such as BF3
Paul G. Wenthold - One of the best experts on this subject based on the ideXlab platform.
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Thermochemical Properties of the Benzynes
Australian Journal of Chemistry, 2010Co-Authors: Paul G. WentholdAbstract:The thermochemical properties of the Benzynes have been the subject of investigation for nearly 50 years. This work provides an overview and assessment of all the experimental thermochemical properties that have been reported for the Benzynes, or can be derived from reported thermochemical data. These properties include enthalpies of formation and thermochemical values that correspond to formation and dissociation of the Benzynes by neutral and ionic processes. Thermochemical values are provided for both the ground-state singlet and the excited-state triplet states of the Benzynes. The starting point for all the thermochemical consideration of the Benzynes are the enthalpies of formation, which, in this work, are recommend to be 107.3 ± 3.5, 121.9 ± 3.1, and 138.0 ± 1.0 kcal mol–1 for ortho-, meta-, and para-Benzyne, respectively (1 kcal mol–1 = 4.184 kJ mol–1). Whereas the paper predominantly focuses on the experimentally determined values, it also provides a comparison with theoretical studies that have examined the absolute thermochemical properties of the Benzynes.
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ultraviolet photoelectron spectroscopy of the o m and p Benzyne negative ions electron affinities and singlet triplet splittings for o m and p Benzyne
Journal of the American Chemical Society, 1998Co-Authors: Paul G. Wenthold, Robert R. Squires, W. C. LinebergerAbstract:The 351 nm photoelectron spectra of the negative ions of o-, m-, and p-Benzyne (1,2-, 1,3-, and 1,4-dehydrobenzene, respectively) and their perdeuterated isotopomers have been obtained. The o-Benzyne ions were generated by the reaction of benzene and benzene-d6 with O-, while the m- and p-Benzyne ions were prepared by the gas-phase reaction between the corresponding 3- and 4-(trimethylsilyl)phenyl anions and molecular fluorine, F2. The photoelectron spectra of the Benzyne anions each contain two features, corresponding to formation of the singlet and triplet states of the biradicals. The electron affinities of o- and p-Benzyne are found to be 0.564 ± 0.007 and 1.265 ± 0.008 eV, respectively, while the electron affinities of deuterated o- and p-Benzyne are found to be 8 and 5 meV lower, respectively. The electron affinity of m-Benzyne could not be determined from the photoelectron spectrum because the origin peak could not be assigned unequivocally. For o- and p-Benzyne, the singlet−triplet energy splittin...
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Ultraviolet Photoelectron Spectroscopy of the o-, m-, and p- Benzyne Negative Ions. Electron Affinities and Singlet−Triplet Splittings for o -, m -, and p -Benzyne
Journal of the American Chemical Society, 1998Co-Authors: Paul G. Wenthold, Robert R. Squires, W. C. LinebergerAbstract:The 351 nm photoelectron spectra of the negative ions of o-, m-, and p-Benzyne (1,2-, 1,3-, and 1,4-dehydrobenzene, respectively) and their perdeuterated isotopomers have been obtained. The o-Benzyne ions were generated by the reaction of benzene and benzene-d6 with O-, while the m- and p-Benzyne ions were prepared by the gas-phase reaction between the corresponding 3- and 4-(trimethylsilyl)phenyl anions and molecular fluorine, F2. The photoelectron spectra of the Benzyne anions each contain two features, corresponding to formation of the singlet and triplet states of the biradicals. The electron affinities of o- and p-Benzyne are found to be 0.564 ± 0.007 and 1.265 ± 0.008 eV, respectively, while the electron affinities of deuterated o- and p-Benzyne are found to be 8 and 5 meV lower, respectively. The electron affinity of m-Benzyne could not be determined from the photoelectron spectrum because the origin peak could not be assigned unequivocally. For o- and p-Benzyne, the singlet−triplet energy splittin...
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Gas‐phase reactions of the Benzyne negative ions
Journal of Mass Spectrometry, 1998Co-Authors: Paul G. Wenthold, Robert R. SquiresAbstract:The reactions of o-, m- and p-Benzyne anions and the phenide ion with a series of neutral reagents are described. The m- and p-Benzyne anions display similar behavior towards Bronsted acids, CS 2 , N 2 O, NO and O 2 , which is analogous to that of phenide ion but clearly different from that of o-Benzyne anion. The strongly basic and nucleophilic character of m- and p-Benzyne anions dominates their reactivity, and radical-type reactions are generally not observed. Novel bifunetional reactions between m- and p-Benzyne anions and both CS 2 and NO are observed in which two sequential S-atom abstractions and two NO additions, respectively, take place.
Tsugio Kitamura - One of the best experts on this subject based on the ideXlab platform.
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Synthetic Methods for the Generation and Preparative Application of Benzyne
Australian Journal of Chemistry, 2010Co-Authors: Tsugio KitamuraAbstract:Many methods have been developed for generating Benzyne. Convenient and reliable precursors extensively studied so far involve benzenediazonium-2-carboxylate and o-dihalobenzenes such as 1,2-bromofluorobenzene and 1,2-dibromobenzene. Recently, in addition to the above precursors, o-(trimethylsilyl)phenyl triflate has been put into frequent use for Benzyne reactions, in which Benzyne is efficiently generated under mild conditions using fluoride ion. Furthermore, o-(trimethylsilyl)phenyliodonium triflate has been developed as a more efficient Benzyne precursor. This mini-review focusses on recent progress in Benzyne chemistry from the viewpoint of organic synthesis. The methods for generating Benzynes are classified by the conditions into four categories: basic conditions using strong bases, mild conditions using fluoride ion, thermolysis, and oxidation.
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Synthesis, Solubility, and Reaction of Long Alkyl-Chained Hypervalent Iodine Benzyne Precursors
Bulletin of the Chemical Society of Japan, 2003Co-Authors: Takayoshi Abe, Teizo Yamaji, Tsugio KitamuraAbstract:Long-chained hypervalent iodine Benzyne precursors bearing ethyl, butyl, hexyl, octyl, decyl, dodecyl, and tetradecyl groups were synthesized, respectively. As the alkyl chain of the Benzyne precursors is lengthened, the solubility in nonpolar organic solvents and the yield of the Benzyne adduct with furan gradually increases.
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reaction of electronically stabilized thiones with Benzyne the isolation of thiobenzophenone Benzyne and thiopivalophenone Benzyne adducts
Bulletin of the Chemical Society of Japan, 2000Co-Authors: Kentaro Okuma, Kyoko Shiki, Shinya Sonoda, Kosei Shioji, Yuji Koga, Tsugio Kitamura, Yuzo Fujiwara, Yoshinobu YokomoriAbstract:The reaction of thiobenzophenones (1) with phenyl[2-(trimethylsilyl)phenyl]iodonium trifluoromethanesulfonate (4) in the presence of tetrabutylammonium fluoride afforded the corresponding [4+2] cycloadducts, which are the first examples of thiobenzophenone-Benzyne adducts. The reaction of thiopivalophenone (6) with Benzyne prepared from 4 and tetrabutylammonium fluoride at room temperature gave [2+2] cycloadducts (7). When the reaction was carried out in refluxing dichloromethane, a mixture of 7 and [4+2] cycloadducts (13) was obtained.
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a new and efficient hypervalent iodine Benzyne precursor phenyl o trimethylsilyl phenyl iodonium triflate generation trapping reaction and nature of Benzyne
Journal of the American Chemical Society, 1999Co-Authors: Tsugio Kitamura, Masakatsu Yamane, Kensuke Inoue, Mitsuru Todaka, Norihiko Fukatsu, And Zhaohong Meng, Yuzo FujiwaraAbstract:A new and efficient hypervalent iodine−Benzyne precursor, (phenyl)[2-(trimethylsilyl)phenyl]iodonium triflate (10), is reported. The hypervalent iodine−Benzyne precursor 10 is readily prepared by reaction of 1,2-bis(trimethylsilyl)benzene with a PhI(OAc)2/TfOH reagent system. Treatment of 10 with Bu4NF in CH2Cl2 at room temperature gives high yields of the Benzyne adducts in the presence of a trapping agent such as furan, 2-methylfuran, anthracene, tetraphenylcyclopentadienone, or 1,3-diphenylisobenzofuran. Especially, the result of the reaction in the presence of furan indicates a quantitative generation of Benzyne and its efficient capture by the furan. Similarly, methylBenzynes (22 and 27) are efficiently generated from the corresponding methyl-substituted (trimethylsilyl)phenyliodonium triflates (12 and 13). The preparation of the hypervalent iodine−Benzyne precursors, the generation of Benzynes, the trapping reactions, and the nature are described in detail together with the advantages of the present...
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A New and Efficient Hypervalent Iodine−Benzyne Precursor, (Phenyl)[o-(trimethylsilyl)phenyl]iodonium Triflate: Generation, Trapping Reaction, and Nature of Benzyne
Journal of the American Chemical Society, 1999Co-Authors: Tsugio Kitamura, Masakatsu Yamane, Kensuke Inoue, Mitsuru Todaka, Norihiko Fukatsu, And Zhaohong Meng, Yuzo FujiwaraAbstract:A new and efficient hypervalent iodine−Benzyne precursor, (phenyl)[2-(trimethylsilyl)phenyl]iodonium triflate (10), is reported. The hypervalent iodine−Benzyne precursor 10 is readily prepared by reaction of 1,2-bis(trimethylsilyl)benzene with a PhI(OAc)2/TfOH reagent system. Treatment of 10 with Bu4NF in CH2Cl2 at room temperature gives high yields of the Benzyne adducts in the presence of a trapping agent such as furan, 2-methylfuran, anthracene, tetraphenylcyclopentadienone, or 1,3-diphenylisobenzofuran. Especially, the result of the reaction in the presence of furan indicates a quantitative generation of Benzyne and its efficient capture by the furan. Similarly, methylBenzynes (22 and 27) are efficiently generated from the corresponding methyl-substituted (trimethylsilyl)phenyliodonium triflates (12 and 13). The preparation of the hypervalent iodine−Benzyne precursors, the generation of Benzynes, the trapping reactions, and the nature are described in detail together with the advantages of the present...
Ernest R. Davidson - One of the best experts on this subject based on the ideXlab platform.
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p Benzyne derivatives that have exceptionally small singlet triplet gaps and even a triplet ground state
Journal of Organic Chemistry, 2003Co-Authors: Aurora E Clark, Ernest R. DavidsonAbstract:In an effort to find a p-Benzyne (1,4-didehydrobenzene) derivative with a triplet ground state, we have investigated tetrasubstitution by −F, −NH2, −CH3, and −NO2 groups. These were predicted to reduce the singlet−triplet gap, but none led to a triplet ground state because of unexpected destabilization of one of the radical orbitals. This effect is likely the result of rehybridization of the substituted C atom, which has been observed for substituted benzene and perturbs the side σ and σ* orbital energies of the phenyl ring. The role of substituent rotation on the energy difference between the two nominally singly occupied orbitals (S and A) was then investigated. The energy of the A radical orbital was found to be much more sensitive to perturbations within the σ C−C framework than the S MO. Consequently, we believe that rehybridization of the ring carbons destabilizes the A radical orbital and can lead to large singlet−triplet splittings. To test this hypothesis, calculations on a p-Benzyne with 2,6 sub...