- Gas phase formation of 1-phenylcyclobuten-3-yl and 1-phenylallyl anions and a determination of the allylic C-H acidities and bond dissociation energies of 1-phenylcyclobutene and (E)-1-phenylpropene
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1-Phenylcyclobuten-3-yl and 1-phenylallyl anions (1a and 2a, respectively) were prepared in the gas phase by deprotonating their conjugate acids in a Fourier transform mass spectrometer. The acidities of both compounds were measured by determining equilib
- Glasovac, Zoran,Eckert-Maksic, Mirjana,Dacres, Jelena E.,Kass, Steven R.
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- Iron-Catalyzed Ring Expansion of Cyclobutanols for the Synthesis of 1-Pyrrolines by Using MsONH3OTf
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The synthesis of 1-pyrrolines from cyclobutanol derivatives and an aminating reagent (MsONH3OTf) has been developed. This one-pot procedure achieves C–N bond/C═N bond formation via ring expansion. A series of 1-pyrroline derivatives are synthes
- Zhuang, Daijiao,Gatera, Tharcisse,An, Zhenyu,Yan, Rulong
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supporting information
p. 771 - 775
(2022/01/20)
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- Lewis-Acid-Catalyzed Tandem Cyclization by Ring Expansion of Tertiary Cycloalkanols with Propargyl Alcohols
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A new method for the efficient synthesis of hexahydro-1H-fluorene and octahydrobenzo[a]azulene derivatives through a ring-expansion strategy is reported. With an appropriate combination of thulium(III) trifluoromethanesulfonate and 13X molecular sieves, a range of unsaturated polycyclic compounds were obtained in good yields. Mechanism studies reveal that the reaction is more likely to undergo Meyer–Schuster rearrangement, ring expansion, and Friedel–Crafts-type pathways, which provide a conceptually different strategy for the ring opening of tertiary cycloalkanols.
- Kong, Xiangtao,Li, Xue-Song,Li, Yuke,Liang, Yong-Min,Liu, Hong-Chao,Niu, Zhi-Jie,Wang, Cui-Tian,Wei, Wan-Xu,Zhang, Zhe
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supporting information
p. 9457 - 9462
(2021/12/14)
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- Palladium-Catalyzed Carbene Coupling Reactions of Cyclobutanone N-Sulfonylhydrazones
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Described herein are the palladium-catalyzed cross-coupling reactions of cyclobutanone-derived N-sulfonylhydrazones with aryl or benzyl halides, suggesting that the metal carbene process and β-hydride elimination can smoothly occur in strained ring system
- Ning, Xiaoqin,Chen, Yongke,Hu, Fangdong,Xia, Ying
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p. 8348 - 8352
(2021/10/25)
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- TFA-Catalyzed [3+2] Spiroannulation of Cyclobutanols: A Route to Spiro[cyclobuta[a]indene-7,1′-cyclobutane] Skeletons
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A straightforward method for the synthesis of spiro[cyclobuta[a]indene-7,1′-cyclobutane] derivatives from cyclobutanols has been developed via one-pot [3+2] spiroannulation. A series of new spiro[cyclobuta[a]indene-7,1′-cyclobutane] derivatives are facile
- An, Zhenyu,Liu, Yafeng,Sun, Yanwei,Yan, Rulong
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p. 3812 - 3815
(2020/10/19)
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- Concurrent Formation of N-H Imines and Carbonyl Compounds by Ruthenium-Catalyzed C-C Bond Cleavage of β-Hydroxy Azides
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A commercial cyclopentadienylrutenium dicarbonyl dimer ([CpRu(CO)2]2) efficiently catalyzes the formation of N-H imines and carbonyl compounds simultaneously from β-hydroxy azides via C-C bond cleavage under visible light. Density functional theory calculations for the cleavage reaction support the mechanism involving chelation of alkoxy azide species and liberation of nitrogen as the driving force. The synthetic utility of the reaction was demonstrated by a new amine synthesis promoted by chemoselective allylation of imine and synthesis of isoquinoline.
- Lee, Jeong Min,Bae, Dae Young,Park, Jin Yong,Jo, Hwi Yul,Lee, Eunsung,Rhee, Young Ho,Park, Jaiwook
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supporting information
p. 4608 - 4613
(2020/06/05)
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- Alkene synthesis by photocatalytic chemoenzymatically compatible dehydrodecarboxylation of carboxylic acids and biomass
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Direct conversion of renewable biomass and bioderived chemicals to valuable synthetic intermediates for organic synthesis and materials science applications by means of mild and chemoselective catalytic methods has largely remained elusive. Development of artificial catalytic systems that are compatible with enzymatic reactions provides a synergistic solution to this enduring challenge by leveraging previously unachievable reactivity and selectivity modes. We report herein a dual catalytic dehydrodecarboxylation reaction that is enabled by a crossover of the photoinduced acridine-catalyzed O-H hydrogen atom transfer (HAT) and cobaloxime-catalyzed C-H-HAT processes. The reaction produces a variety of alkenes from readily available carboxylic acids. The reaction can be embedded in a scalable triple-catalytic cooperative chemoenzymatic lipase-acridine-cobaloxime process that allows for direct conversion of plant oils and biomass to long-chain terminal alkenes, precursors to bioderived polymers.
- Nguyen, Vu T.,Nguyen, Viet D.,Haug, Graham C.,Dang, Hang T.,Jin, Shengfei,Li, Zhiliang,Flores-Hansen, Carsten,Benavides, Brenda S.,Arman, Hadi D.,Larionov, Oleg V.
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p. 9485 - 9498
(2019/10/11)
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- The cyclopropylcarbinyl route to γ-silyl carbocations
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The mesylate derivative of cis-1-hydroxymethyl-2-trimethylsilylcyclopropane has been prepared, along with a number of related mesylates and triflates with substituents on the 1-position. These substrates all solvolyze in CD3CO2D to give products derived from cyclopropylcarbinyl cations that undergo further rearrangement to give 3-trimethylsilylcyclobutyl cations. These 3-trimethylsilylcyclobutyl cations are stabilized by a long-range rear lobe interaction with the γ-trimethylsilyl group. When the substituent is electron-withdrawing (CF3, CN, or CO2CH3), significant amounts of bicyclobutane products are formed. The bicyclobutanes are a result of γ-trimethylsilyl elimination from the cationic intermediate that has an unusually long calculated Si-C bond. The solvolysis chemistry of mesylate and triflate derivatives of trans-1-hydroxymethyl-2-trimethylsilylcyclopropane and 1-substituted analogs can be quite different since these substrates do not generally lead to 3-trimethylsilylcyclobutyl cations.
- Creary, Xavier
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p. 1769 - 1780
(2019/08/07)
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- Studies in Acyl C-H activation via aryl and alkyl to acyl "through space" migration of palladium
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Examples of the 1,4-migration of a palladium moiety in aryl- and alkylpalladium intermediates to the acyl position of an aldehyde or formamide have been observed. The resulting acylpalladium intermediate can undergo ester or carbamate formation by reaction with an alcohol; decarbonylation, followed by β hydride elimination to an alkene; reaction with an organomercurial to form an ester; or alkene insertion. Deuterium-labeling studies have been used to confirm the palladium migration mechanism.
- Kesharwani, Tanay,Verma, Akhilesh K.,Emrich, Daniel,Ward, Jeffrey A.,Larock, Richard C.
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supporting information; experimental part
p. 2591 - 2593
(2009/10/23)
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- Phenyl versus alkyl migration in the fragmentation of alkoxychlorocarbenes
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Phenyl versus methyl (alkyl) group migration is assessed in the fragmentations of neophyloxychlorocarbene, 2,2-diphenylpropyloxychlorocarbene, and 1-phenylcyclopropylmethoxychlorocarbene. Rate constants and activation parameters of the fragmentations are also reported.
- Moss, Robert A.,Fu, Xiaolin
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p. 235 - 237
(2007/10/03)
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- Experimental determination of the heat of hydrogenation of phenylcyclobutadiene
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The heat of hydrogenation of phenylcyclobutadiene (ΔH° hyd = 57.4 ± 4.9 kcal mol-1) was determined via a thermodynamic cycle by carrying out gas-phase measurements on 1-phenylcyclobuten-3-yl cation. This leads to an antiaromatic destabilization energy of 27 ± 5 kcal mol-1, a difference of 9.6 ± 4.9 kcal mol-1 for the first and second C-H bond dissociation energies of 1-phenylcyclobutene, and an estimate of 96 ± 5 kcal mol-1 for the heat of formation of cyclobutadiene. These results are compared to G3, G3(MP2), and B3LYP computations and represent the first experimental measurements of the energy of a monocyclic cyclobutadiene.
- Fattahi, Alireza,Lis, Lev,Kass, Steven R.
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p. 13065 - 13069
(2007/10/03)
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- Laser flash photolysis study of arylcyclopropylcarbenium ions: Cation stabilizing abilities of cyclopropyl and phenyl groups
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Arylcyclopropylcarbenium ions, Ar(c-Pr)CH+, were generated as transient intermediates by laser flash photolysis (LFP) of trans-2,3-diphenylaziridinimines of aryl cyclopropyl ketones in 2,2,2-trifluoroethanol (TFE). The carbocations are thought to arise by way of diazo compounds and carbenes. Rate constants for the unimolecular decay in TFE and for the bimolecular reaction with methanol in TFE were obtained for Ar(c-Pr)CH+ and for analogous arylphenylcarbenium ions, ArPhCH+. Within these series, the cation stabilizing abilities of cyclopropyl and phenyl groups are found to be similar in magnitude. However, cyclopropyl responds more strongly than phenyl to increasing electron demand. Hence cyclopropyl is superior to phenyl in cation stabilizing ability for Ar = Ph but inferior to phenyl for Ar = 4-MeOC6H4.
- Kirmse, Wolfgang,Krzossa, Birgit,Steenken, Steen
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p. 7473 - 7477
(2007/10/03)
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- Cyclobutene photochemistry. Substituent effects on the photochemistry of 1-phenylcyclobutene
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The photochemistry and photophysic of 1-phenylcyclobutene and five aryl-substituted derivatives have been studied in various solvents at room temperature.All six compounds fluoresce with quantum yields in the 0.2-0.3 range in cyclohexane and acetonitrile solution. 1-Phenylcyclobutene undergoes -cycloreversion (γ = 0.09) to yield phenylacetylene upon photolysis in either hydrocarbon or acetonitrile solution, and undergoes (Markovnikov) solvent addition upon irradiation in methanol solution (γ = 0.08) in addition to cycloreversion.Triplet sensitization and quenching experiments indicate that cycloreversion and methanol addition are both excited singlet state processes.None of the six compounds studied undergo ring opening to the corresponding 2-aryl-1,3-butadiene in detectable yield.Quantum yields for cycloreversion in cyclohexane, acetonitrile, and methanol solution and methanol addition have been determined for the six compounds, along with excited singlet state lifetimes.The quantum yields and rate constants for cycloreversion and methanol addition are both enhanced by substitution with electron-donating groups.The variation in the rate constant for cycloreversion with substituent indicates that there is substantial dipolar character developed in the cyclobutenyl ?-bond framework during the reaction, in almost exact correspondence with that developed in the ? system during photoprotonation.No deuterium scrambling is observed in 1-phenylcyclobutene-2,4,4-d3 after photolysis in pentane solution to ca. 80percent conversion, indicating that sleletal rearrangements leading to cyclopropyl carbenes do not occur in the direct photolysis of arylcyclobutene derivatives.A pericyclic mechanism for the photocycloreversion reaction is suggested.Triplet-triplet absorption spectra and triplet lifetimes of 1-phenyl-, 1-(para-methylphenyl)-, and 1-(para-trifluoromethylphenyl)cyclobutene in hydrocarbon solution are also reported. Key words: photochemistry, cyclobutene, fluorescence, -cycloreversion, substituent effects, nanosecond laser flash photolysis, lifetime, triplet state, styrene, photoaddition
- Leigh, William J.,Postigo, J. Alberto
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p. 191 - 203
(2007/10/02)
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- 1,2-Hydrogen migration and alkene formation in the photoexcited states of alkylphenyldiazomethanes
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Laser flash photolysis of alkylphenyldiazomethanes in the presence of pyridine produces easily detected ylides. The data indicate that photolysis of alkylphenyldiazomethanes leads to both carbene formation and direct formation of rearrangement products which do not derive from relaxed carbene intermediates.
- ?elebi, Sol,Leyva, Soccoro,Modarelli, David A.,Platz, Matthew S.
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p. 8613 - 8620
(2007/10/02)
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- Ring-Formation from Allyl- and Vinylstannanes Initiated by Treatment with Butyl-Lithium
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The allylstannane 1 and the vinylstannane 3, 5 and 7 cyclise when treated with butyl-lithium.
- Barbero, Asuncion,Cuadrado, Purificacion,Gonzalez, Ana M.,Pulido, Francisco J.,Rubio, Rosa,Fleming, Ian
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p. 5841 - 5842
(2007/10/02)
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- Studies on the Oxidation of Phenyl Cycloalkanes by Tertiary Hydroperoxides
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During the thermal decomposition of cumene hydroperoxide at about 125 deg C in phenyl cycloalkanes as solvents, the solvents are attacked, preferably at the tertiary C-H bonds.Up to 70percent (with regard to the decomposed hydroperoxide) of oxidation products of the phenyl cycloalkanes are obtained.The main oxidation products are the corresponding 1-phenyl cycloalkanols, but relatively large amounts of phenyl alkyl ketones with the same number of carbon atoms are also formed, probably via a further oxidation of the 1-phenyl cycloalkanols.
- Pritzkow, Wilhelm,Suprun, Vladimir Ya.,Voerckel, Volkmar
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p. 381 - 386
(2007/10/02)
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- Studies on the Autoxidation of Phenyl Cycloalkanes
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The products of the autoxidation of phenyl cyclopropane (I), phenyl cyclobutane (II), phenyl cyclopentane (III), phenyl cyclohexane (IV), phenyl cycloheptane (V) and phenyl cyclooctane (VI) were analyzed after reduction of the reaction mixtures with LiAlH4.As products of the attack on the α-C-H bonds the corresponding 1-phenyl cycloalkanols and 1-phenyl alkan-1-ols were found.In the case of phenyl cyclopropane some SR2 ring opening probably takes place.The oxidabilities , the chain termination constants kt, the absolute chain propagation constants kp and the relative chain propagation constants (kp)rel were determined for the phenyl cycloalkanes I-VI.As it is to be expected on the basis of the I-strain concept the autoxidation rate of phenyl cyclopentane (III) is considerably higher than that of phenyl cyclobutane (II) and phenyl cyclohexane (IV).
- Batke, Birgit,Lauterbach, Gerlinde,Pritzkow, Wilhelm,Voerckel, Volkmar,Belyakov, Vladimir A.
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p. 424 - 430
(2007/10/02)
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- In search of α-eliminations of carbon induced by sixteen electron iron: photolysis and thermolysis of derivatives of phenyl substituted cyclobutanes and cyclopropanes
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Photolysis of dicarbonyl(ε5-cyclopentadienyl)(1-phenylcyclobutane-1-carbonyl)iron is proposed to give the hydride complex Ph(cyclobutenyl)Fe(Cp)(CO)H which dissociates to 1-phenylcyclobutene and FpH (Fp = ε5-cyclopentadienyldicarbonyliron).The FpH complex can oxidatively add to the sixteen electron acyl or ? complexes (Ph(cyclobutyl)-C(O)FeCp(CO) and Ph(cyclobutyl)FeCp(CO) respectively) to produce phenylcyclobutane and 1-phenylcyclobutane carboxaldehyde.Photolysis of dicarbonyl(ε5-cyclopentadienyl)(1-phenylcyclopropyl-1-carbonyl)iron gives a ? complex with no further reaction.Substitution of CO with PPh3 and thermolysis producrally substituted ?-allyl complex.In neither the cyclobutyl nor the cyclopropyl case did the reactions give isolable carbene complexes; apparently the phenyl substituent does not provide adequate stabilization of the carbene complex to allow its detection or isolation.
- Trace, Rhonda,Jones, W. M.
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p. 103 - 114
(2007/10/02)
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- CYCLOPROPYLPHENYLCARBENE-THERMAL CONTROL OF INTERMOLECULAR ADDITION
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At 25deg C, photolytically generated cyclopropylphenylcarbene affords phenylcyclobutene (63percent, by ring expansion), phenylacetylene (16percent, by fragmentation), and only traces (3percent) of the adduct to isobutene; at lower temperatures, however, the latter compound becomes the major product.
- Moss, Robert A.,Wetter, William P.
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p. 997 - 1000
(2007/10/02)
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