4087-50-7Relevant articles and documents
Geminal repulsion disrupts Diels–Alder reactions of geminally substituted cyclopentadienes and 4H-pyrazoles
Levandowski, Brian J.,Abularrage, Nile S.,Raines, Ronald T.
, (2021)
We have experimentally and computationally explored the sluggish Diels–Alder reactivities of the geminally substituted 5,5-dimethylcyclopentadiene and 5,5-dimethyl-2,3-diazacyclopentadiene (4,4-dimethyl-4H-pyrazole) scaffolds. We found that geminal dimethylation of 1,2,3,4-tetramethylcyclopentadiene to 1,2,3,4,5,5-hexamethylcyclopentadiene decreases the Diels–Alder reactivity towards maleimide by 954-fold. Quantum mechanical calculations revealed that the decreased Diels–Alder reactivities of gem-dimethyl substituted cyclopentadienes and 2,3-diazacyclopentadienes are not a consequence of unfavorable steric interactions between the diene and dienophile as reported previously, but a consequence of the increased repulsion within the gem-dimethyl group in the transition state. The findings have implications for the use of cyclopentadienes in “click” chemistry.
Highly efficient chiral 2-oxazolidinone auxiliaries derived from methylcyclopentadienes and 2-oxazolone
Hashimoto, Noriaki,Ishizuka, Tadao,Kunieda, Takehisa
, p. 721 - 724 (1994)
Sterically congested [4+2]cycloadduct-based 2-oxazolidones, (1R,2R,6S,7S)-1, 7, 8, 9, 10, 10-hexamethyl- and (1S,2R,6S,7S,10R)-1, 7, 8, 9, 10, 10-pentamethyl-3-oxa-5-azatricyclo[5.2.1.02,6]dec-8-en-4-ones and their enantiomers, derived from hex
Molecular Solar Thermal Batteries through Combination of Magnetic Nanoparticle Catalysts and Tailored Norbornadiene Photoswitches
Lorenz, Patrick,Luchs, Tobias,Hirsch, Andreas
supporting information, p. 4993 - 5002 (2021/02/26)
Cobalt catalysts are immobilized on the surface of iron oxide nanoparticles for the preparation of highly active quasi-homogeneous catalysts toward an efficient release of photochemically stored energy in norbornadiene-based photoswitches. The facile sepa
Oxygen atom insertion into iron(II) phenyl and methyl bonds: A key step for catalytic hydrocarbon functionalization
Mei, Jiajun,Pardue, Daniel B.,Kalman, Steven E.,Gunnoe, T. Brent,Cundari, Thomas R.,Sabat, Michal
, p. 5597 - 5605 (2015/02/19)
Oxy-functionalization of metal-alkyl and ?aryl bonds is a key step in potential hydrocarbon oxidation catalysis. However, well-defined examples of M-R to ROH conversion are rare, especially for first-row transition metals. CpFe(CO)(NCMe)Ph reacts with oxygen or hydrogen peroxide to produce benzoic acid. Removing CO from the CpFe(L)(L')Ph framework allows simple oxygen atom insertion into the Fe-Ph bond. CpFe(P(OCH2)3CEt)2Ph reacts with Me3NO in THF to produce PhOH in high yield when Bronsted acids are added. Studies show that light promotes P(OCH2)3CEt dissociation from CpFe(P(OCH2)3CEt)2Ph, which facilitates the conversion to PhOH. The methyl analogue CpFe[P(OCH2)3CEt]2Me reacts with oxidants to produce MeOH.
PHASE TRANSFER CATALYZED TERT-ALKYLATIONS OF CYCLOPENTADIENE AND INDENE: INDICATIONS FOR SET PROCESSES
Dehmlow, Eckehard V.,Bollmann, Christof
, p. 5773 - 5776 (2007/10/02)
Scope and mechanism of the PTC tert-alkylation of cyclopentadienide anion have been investigated.On the side of the anion, the reaction is limited to cyclopentadiene and indene, whereas many tertiary as well as secondary and primary alkylating agents can be employed.Hexamethylcyclopentadiene 8, for instance, is available easily.Tert-alkylations of this type are more effective if 4,4'-bipyridinium salts are present in addition to a phase transfer catalyst.The reactions involve probably an initial single electron transfer (SET) step.
Organolanthanide and organoactinide oxidative additions exhibiting enhanced reactivity. 5. Stoichiometry, kinetic, and mechanistic studies of (C5Me5)2YbII·OEt2 oxidative-addition reactions and of (C5Me5)2YbIIIR (R = R, X) YbIII ...
Finke,Keenan,Watson
, p. 263 - 277 (2008/10/08)
Full title: Organolanthanide and organoactinide oxidative additions exhibiting enhanced reactivity. 5. Stoichiometry, kinetic, and mechanistic studies of (C5Me5)2YbII·OEt2 oxidative-addition reactions and of (C5Me5)2YbIIIR (R = R, X) YbIII-Grignard reactions with alkyl and aryl halides. Evidence for the dominance of inner-sphere mechanisms. (C5Me5)2YbII·OEt 2 undergoes atom-abstraction oxidative addition with alkyl and aryl halides according to the generalized stoichiometry 1.0(C5Me5)2YbII·OEt 2 + (1 + a)RX → (1 - a)(C5Me5)2YbIIIX + (a)(C5Me5)1YbIIIX2 + (a)C5Me5R + 1.0Et2O + 1.0[R-R, R-H(alkanes), R(-H)(olefins)]. A reactive Yb-alkyl intermediate, (C5Me5)2YbIIIR, is formed from R? trapping by diamagnetic (C5Me5)2YbII. This (C5Me5)2YbIIIR intermediate and the initial product (C5Me5)2YbIIIX react further with RX in subsequent YbIII-Grignard reactions that are retarded by added Et2O and, therefore, apparently operate via an inner-sphere pathway. The observed YbIII-Grignard stoichiometries are (C5Me5)2YbIIIR + 2RX → (C5Me5)2YbIIIX2 + C5Me5R + R-R and (C5Me5)2YbIIIX + RX → (C5Me5)1YbIIIX2 + C5Me5R. The absolute rates of reaction of RX with (C5Me5)2YbII·OEt2 are found to be first-order each in (C5Me5)2YbII·OEt-2 and RX, with an added inverse dependence upon Et2O. The Et2O dependence is consistent with a requirement for a site of coordinative unsaturation and an inner-sphere pathway. Comparison of the rates of reactions of (C5Me5)2UIII(Cl)(THF) and (C5Me5)2YbII·OEt2 with RX provides compelling evidence for participation of electron transfer in these net atom-abstraction reactions.
Inductive Effects in Neighboring-Group Participation. Destabilization of Carbocations by CC Double Bonds in Solvolyses of 2,2,5,5-Tetramethylcyclopent-3-en-1-yl Tosylates
Bentley, T. William,Irrgang, Bernhard,Mayr, Herbert,Schleyer, Paul von Rague
, p. 3492 - 3498 (2007/10/02)
The possibility of homoallylic participation in solvolyses of substituted cyclopent-3-en-1-yl sulfonates has been investigated.Relative rates of solvolyses of 2,2,5,5-tetramethylcyclopentyl (6), 2,2,3,4,5,5-hexamethylcyclopent-3-en-1-yl (13), 2,2,5,5-tetramethyl-3,4-bis(methylene)cyclopent-1-yl (16), and 2,2,5,5-tetramethylcyclopent-3-en-1-yl (18) tosylates in 80percent (v/v) ethanol/water at 95 deg C are 128:5.9:5.4:1.Measures of solvent effects on the reactivity of tetramethylcyclopentyl tosylate 6 (m = 0.88, Q' = 0.94) confirm the expectation that nucleophilic solvent participation (if any) is very week, and the large destabilizing effect of the double bond in the cyclopent-3-en-1-yl cation, predicted by theoretical calculation, is now confirmed experimentally.Diene products arising from 1,2-methyl shifts dominate.Solvolytic data in weakly nucleophilic media (e.g., hexafluoroisopropyl alcohol) show that β-methyl and β,β-dimethyl substitution increase the solvolysis rate of cyclopenyl tosylate cumulatively, but the tetramethyl derivative shows anomalously low reactivity, possibly due to steric inhibition of solvation and of departure of the leaving group.
AN ELECTRON SPIN RESONANCE STUDY OF CYCLOPENTADIENE RADICAL CATIONS
Courtneidge, John L.,Davies, Alwyn G.,Shields, Charles J.,Yazdi, Satieh N.
, p. 799 - 806 (2007/10/02)
If solutions of hexa-, penta-, tetra-, or tri-alkylcyclopentadienes in trifluoroacetic acid are irradiated with u.v. light, the e.s.r. spectra of the corrasponding alkylcyclopentadiene radical cations can be observed.The radical cation Me5C5H+. can also be obtained from decamethylbi(cyclopentadienyl), Me5C5-C5Me5, under similar conditions.The spectra of Me6C5+., Me5C5H+., and Me4C5H2+. can be analysed in terms of single isomers.The sp3 carbon atom of the ring lies in the nodal plane of the SOMO, and substituents at this position show only small hyperfine coupling constants.The radical cation Me5C5H+. shows no evidence of fluxionality on the e.s.r. timescale up to 328 K.The spectra of Me4EtC5H+., Me3Et2C5H+., and Me3C5H3+. apparently relate to mixtures of prototropic isomers.Experiments with optical cut-off filters show that the primary photochemical process involves excitation of the protonated diene.
The Homolysis of C-H Bonds in Carbocations
Chan, Wang,Courtneidge, John L.,Davies, Alwyn G.,Djap, Woei Haw,Gregory, Peter S.,Yazdi, Safieh N.
, p. 1541 - 1542 (2007/10/02)
The e.s.r. spectra of certain tetra-alkylcyclobutadiene radical cations, of the hexamethylcyclopentadiene radical cation, and of various polycyclic aromatic radical cations, RH.+, are observed when the corresponding hydrocarbon cations, RH2+, are photolysed in trifluoroacetic acid solvent.
