91-12-3Relevant academic research and scientific papers
Synthetic and Theoretical Studies of Cyclobuta[1,2:3,4]dicyclopentene. Organocobalt Intermediates in the Construction of the Unsaturated Carbon Skeleton and Their Transformation into Novel Cobaltacyclic Complexes by C-C Insertion
Myers, Andrew G.,Sogi, Miki,Lewis, Michael A.,Arvedson, Stephen P.
, p. 2516 - 2525 (2007/10/03)
Theoretical and synthetic studies of the tricyclic 10π-electron hydrocarbon cyclobuta[1,2:3,4]-dicyclopentene (1), a nominally aromatic structure that has never been synthesized, are described. Geometry optimization by density-functional-theory calculatio
Photochemistry of matrix-isolated cyclopentadienylidene revisited
Maier,Endres
, p. 179 - 187 (2007/10/03)
Irradiation of diazocyclopentadiene (1) in a matrix at 10 K with the wavelength λ = 366 nm leads - as already known - to rapid loss of nitrogen and the formation of cyclopentadienylidene (T-2). Upon photoexcitation of cyclopentadienylidene (2) with light of the wavelength λ = 313 nm the (s-E)-(E)-conformer of 2-penten-4-yn-1-ylidene (T-7a) can be detected, which is effectively converted into 3-ethynylcyclopropene (6) by using light with a wavelength of λ = 436 nm. The structural elucidation of T-7a and 6 is based on the comparison of the experimental and calculated IR spectra. Irradiation of cyclopentadienylidene (2), isolated together with the eliminated nitrogen in the same matrix cage, with light of wavelengths longer than 570 nm initiates a partial back-reaction to the starting material, diazocyclopentadiene (1) by recapturing the evolved nitrogen molecule.
The reactions of diazo compounds with lactones. Part 1. Cyclopropanespiro-β-lactones from diketene: Synthesis and reactions
Murphy, Paul V.,O'Sullivan, Timothy J.,Geraghty, Niall W.A.
, p. 2109 - 2119 (2007/10/03)
The cyclopropanespiro-β-lactones 3, 4 and 12 can be prepared by the metal catalysed, or photochemically promoted decomposition reactions of diazocompounds in the presence of diketene. The thermal reactions of these compounds give a variety of products depending on the nature of the spirolactone; these include a furan 9a, 1,4-dicarbonyl compounds 18a-c and 19b, a pyranone 20b, furanones 21a, 21f and 22a and the enol 16. The boron trifluoride promoted reaction of a mixture of 3b and 4b gives a 13-ketoacid. Mechanisms are proposed for the formation of these products. The rearrangment of the cyclopropanespiro-β-lactones to furan-2(5H)-ones and furan-2-(3H)-ones 6-8, 21a, 21f, 22a and 24 is shown to be a general reaction that involves metal catalysis. A mechanism based on formation of a metallocycle by a novel insertion of the metal into the C-O bond of the β-lactone ring is proposed for this rearrangement. This accounts for the observed features of the reaction.
DIRECT IR-SPECTROSCOPIC OBSERVATION OF (1+2)-CYCLOADDITION OF CYCLOPENTADIENYLIDENE TO ETHYLENE IN ARGON MATRIX
Nefedov, Oleg M.,Zuev, Petr S.,Maltsev, Andrey K.,Tomilov, Yuri V.
, p. 763 - 764 (2007/10/02)
Cyclopentadienylidene was generated in argon matrix doped with 2percent C2H4 and the direct reaction of the carbene with C2H4 in matrix, when it was annealing from 12 to 40-45 K, was observed.
Synthesis of Pentafulvalene by Oxidative Coupling of Cyclopentadienide with Copper(II) Chloride
Escher, Andre,Rutsch, Werner,Neuenschwander, Markus
, p. 1644 - 1654 (2007/10/02)
Starting with a nearly quantitative coupling of cyclononatetraenide 7 to 1,1'-dihydrononafulvalene 8 by means of AgBF4, a simple general synthetic concept for fulvalenes is outlined (Scheme 2), consisting in an oxidative coupling of 'Hueckel anions' like 2 and 7 to 1,1'-dihydrofulvalenes 10 with Ag(I) or Cu(II) salts, followed by deprotonation (->11) and oxidation (->12); it has been realised in the case of pentafulvalene (1; overall yield 61percent; Scheme 3) and 1,2:5,6-dibenzopentafulvalene (18; overall yield 66percent; Scheme 4).NMR-spectroscopic investigations show that 1 is a non-aromatic compound with strongly alternating bond-lengths, its ?-system being even more localised than that of simple pentafulvenes.In fact, 1 is extremely reactive in concentrated solutions above -50 deg C.Besides of polymerisations, Diels-Alder dimerisation 1->19 followed by a rearrangement 19->20 takes place (Scheme 5).
Cyclopentadienylidene. A Matrix Isolation Study Exploiting Photolysis with Unpolarized and Plane-Polarized Light
Baird, Mark S.,Dunkin, Ian R.,Hacker, Nigel,Poliakoff, Martyn,Turner, James J.
, p. 5190 - 5195 (2007/10/02)
Diazocyclopentadiene (1) was photolyzed in N2, CO, and other low-temperature matrices.The resulting carbene, cyclopentadienylidene (2), was characterized by its UV and IR spectra, and its thermal dimerization and reaction with CO were observed.Photolysis of 1 with plane-polarized light gave matrices exhibiting linear dichroism.Comparison of dichroic IR and UV spectra revealed that the photolysis proceeds via an excited A1 state of the diazo compound.Plane-polarized irradiation of the corresponding ketene (4) in CO matrices resulted in photoreorientation of the molecules of 4 without significant loss.
THE ELECTRON SPIN RESONANCE SPECTRUM OF THE FULVALENE RADICAL ANION
Davies, Alwyn G.,Giles, Jeremy R. M.,Lusztyk, Janusz
, p. 747 - 752 (2007/10/02)
The fulvalene radical anion has been prepared by the oxidation of cyclopentadienyl-lithium or dilithium fulvalenediide with oxygen, and by the reduction of fulvalene with sodium, or electrolytically.The e.s.r. spectrum shows a( H-2,-2',-5,-5' ) 1.55, a( H-3,-3',-4,-4' ) 3.70, a( 13C-1,-1' ) 2.90, a( 13C-2,-2',-5,-5' ) 1.40, and a( 13C-3,-3',-4,-4' ) 2.15 G.The assignments for a(H) are based on the HMO model, and those for a( 13C ) on the Yonezawa-Kawamura-Kato relationship.
Hypovalent Radicals. 4. Gas-Phase Studies of the Ion-Molecule Reactions of Cyclopentadienylidene Anion Radical in a Flowing Afterglow
McDonald, Richard N.,Chowdhury, A.Kasem,Setser, D.W.
, p. 6491 - 6498 (2007/10/02)
The carbene anion radical, cyclopentadienylidene-.(c-C5H4-., 1), was generated by dissociative electron attachment with diazocyclopentadiene (2) in a flowing afterglow apparatus.The ion-molecule reaction of 1 with 2 produced c-C5H4N=N-c-C5H4-., c-C5H4=c-C5H4-., and c-C5H5- by coupling at Nβ and C1 of 2 and H. abstraction from 2, respectively.The PA(1) = 377 +/- 2 kcal mol-1 was determined from bracketing reactions of ROH + 1 -> RO- + c-C5H5., which gives ΔHf0(1) = 70.7 +/- 3.2 kcal mol-1.Although the H. abstraction process by 1 was observed in most of its ion-molecule reactions, 1 failed to react with CH4, C2H4, and c-C3H6 probably because of an activation barrier of (*) 3 kcal mol-1 in these cases.With dipolar CH3OH and 1, the only observed reaction was H. abstraction from the O-H bond (shown with CH3OD).This lower limit of the H. affinity of 1 gives ΔHf0(1) (*) 67.7 +/- 3 kcal mol-1, in excellent agreement with the value derived from protonation studies.The reactions of 1 with CH3X (Cl, Br) occur by H. abstraction and halide ion (SN2) displacement.Anion radical 1 adds to activated olefins H2C=CHX (CN, CO2CH3, Cl) by a nucleophilic Michael addition mechanism.The EA of the carbene c-C5H4 was bracketed by charge-transfer reactions between 1 and C6F6 and NO2.All of these and certain other results are consistent with the ?1?2 electronic configuration as the ground state of 1.The reactions of 1 with alcohols are postulated to proceed via a hydrogen-bonded complex.
