1076-69-3Relevant academic research and scientific papers
Telomers of Bent Arenes. Acid-Catalyzed Dimerization and Trimerization of the 1,4-Hexamethylene-Bridged Arenes Paracyclophane, (1,4)Napthalenophane, and (1,4)Anthracenophane
Tobe, Yoshito,Jimbo, Mamoru,Kobiro, Kazuya,Kakiuchi, Kiyomo
, p. 5241 - 5243 (1991)
Whereas treatment of 1,4-hexamethylene-bridged benzene paracyclophane (1) with a catalytic amount of H2SO4 gave, as a minor product, dimer 6, along with isomers 4 and 5, similar treatment of 1,4-hexamethylene-bridged naphthalene (1,4)naphthalenophane (2) afforded predominantly dimers 7 and 8, together with trimers 9 and 10.The 1,4-hexamethylene-bridged anthracene (1,4)anthracenophane (3) yielded only trimers 13 and 14.
A NEW EFFICIENT SYNTHESIS AND REARRANGEMENTS OF PARACYCLOPHANE
Tobe, Yoshito,Ueda, Ken-ichi,Kakiuchi, Kiyomi,Odaira, Yoshinobu
, p. 1645 - 1646 (1983)
paracyclophane (1) has been synthesized by oxidative decarboxylation of propellenecarboxylic acid with lead tetraacetate.Vapor phase thermolysis of 1, affords 3-methylenespiroundeca-1,4-diene predominantly, while acid-catalyzed rearrangement of 1 gives the meta and ortho isomers in ratio of 1:3.
Absence of Intersystem Crossing in 1,4-Didehydrobenzene
Lott, William B.,Evans, Tom J.,Grissom, Charles B.
, p. 2583 - 2586 (2007/10/02)
The rate of singlet-to-triplet intersystem crossing in 1,4-didehydrobenzene (the biradical produced as a reactive intermediate in the thermal cycloaromatization of enediynes), cannot be increased by the application of an external magnetic field.The rate of product formation and the distribution of stable products of 2,3-di-n-propyl-1,4-didehydrobenzene thermolysis is unchanged at magnetic flux densities in the range 0-2000 G and at 66 000 G.Similarly, the rate of thermolysis of an unsymmetrical enediyne is insensitive to magnetic field flux in the same range.This finding precludes the modulation of enediyne reaction rates in pharmaceutical and synthetic pursuits.
Unusual reactivity of bent acenes: Reactions of [6](1,4)naphthalenophane and [6](1,4)anthracenophane with electrophiles
Tobe, Yoshito,Takemura, Akihiro,Jimbo, Mamoru,Takahashi, Tohru,Kobiro, Kazuya,Kakiuchi, Kiyomi
, p. 3479 - 3491 (2007/10/02)
The unusual reactivity of [6](1,4)naphthalenophane (2) and [6](1,4)anthracenophane (3), the smallest-bridged acenophanes hitherto known, in electrophilic reactions has been disclosed. These reactions include (i) acid-catalyzed telomerization, (ii) peracid
SYNTHESIS, STRUCTURE AND REACTIVITIES OF PARACYCLOPHANES
Tobe, Yoshito,Ueda, Ken-ichi,Kakiuchi, Kiyomi,Odaira, Yoshinobu,Kai, Yasushi,Kasai, Nobutami
, p. 1851 - 1858 (2007/10/02)
The synthesis, structure and reactivities of paracyclophanes 2a-c, the smallest bridged paracyclophanes so far isolated, are described.The parent hydrocarbon 2a has been efficiently synthesized by oxidative decarboxylation of propellenecarboxylic acid (7) by lead tetraacetate.The 8-carbomethoxy derivative 2b has been quantitatively synthesizedby thermal valence isomerization of the propelladiene (4b) (Dewar isomer of 2b).X-Ray structure analysis of the crystalline 2c has revealed that the benzene ring of 2c is severely deformed into a boat conformation with deformation angles of α=20.5 degree and β=18.5 degree.Furthermore, the bond angles of the bridging chain (C(2), C(3), C(4) and C(5)) are considerably expanded from the normal sp3 angle.Vapor phase thermolysis of 2a gives the spiro triene 12 via homolysis at the benzyl position.Acid-catalyzed isomerization of 2a with trifluoroacetic acid takes place readily to afford the meta and ortho isomers 13a and 14a in a ratio of 1:3.UV irradiation of the ester 2b brings about valence isomerization to the Dewar isomer 4b which izomerizes slowly to the prismane derivative 15a on further irradiation.A cycloaddition of 2a with N-phenyl-1,2,4-triazoline-3,5-dione occurs at room temperature to give mainly adduct 16.Addition of bromine to 2a takes place to furnish quantitatively the unstable 1,4-addition product 18.Oxidation of 2a with mCPBA readily takes place to give the dienone dimer 20 which affords on UV irradiation the cage diketone 21 derived from intramolecular photocycloaddition.
A comparative investigation of 1,4-pentamethylene and 1,4-hexamethylene Dewar benzene. Evidence for the intermediate formation of paracyclophane
Straten, J. W. van,Turkenburg, L. A. M.,Wolf, W. H. de,Bickelhaupt, F.
, p. 89 - 97 (2007/10/02)
The synthesis of the title compounds 1a and 1b is described.Starting from the corresponding 1,2-dimethylenecycloalkanes 6, the compounds 1 were obtained in four steps, viz. addition of dichlorocarbene, reduction with triphenyltin hydride, treatemnt with potassium tert-butoxide and silver-ion-catalyzed rearrangement.In the last step, the 1,2-isomers 11 of 1 were also formed, and their thermal rearrangement to the benzocycloalkenes 4 is briefly described.Compound 1b rearranged to its aromatic isomer (6)paracyclophane (2b) both thermally (60 deg C in solution, 100-460 deg C flow pyrolysis) and under silver-ion catalysis at room temperature; in this latter reaction the initially formed 2b was gradually further isomerized to 4b.At higher temperatures, 2b rearranged to the spirotrienes 3b and finally fragmented to give p-ethylstyrene (17).From 1a, the spirotriene 3a and benzocycloheptene (4a) were obtained by thermolysis and by silver-ion catalysis, respectively.The mechanism of these reactions is discussed and it is concluded that (5)paracyclophane (2a) is a transient intermediate in th reaction of 1a.
Kinetic Investigations of Diels - Alder - Reactions of Cyclooctyne with Consecutive Aromatization
Molz, Thomas,Koenig, Peter,Goes, Robert,Gauglitz, Guenter,Meier, Herbert
, p. 833 - 839 (2007/10/02)
The tricyclic compounds 3a - g, generated from cyclooctyne (1) and the cyclic dienes 2a - g, show a totally different stability. 3a, b, f, and g decompose spontaneously.By elimination of CO2, SO2, CO, and N2, respectively, the aromatic systems 4a - c are formed. 3c loses C2H4 on heating. 3e is thermally cleaved only to a very small extent, but efficiently in the photolysis and finally 3d is stable against aromatization.Detailed kinetical measurements are performed of the thermal elimination of ethylene and of the photochemical bisdecarbonylation.
Kinetic Evidence for the Formation of Discrete 1,4-Dehydrobenzene Intermediates. Trapping by Inter- and Intramolecular Hydrogen Atom Transfer and Observation of High-Temperature CIDNP
Lockhart, Thomas P.,Comita, Paul B.,Bergman, Robert G.
, p. 4082 - 4090 (2007/10/02)
Upon being heated, alkyl-substituted cis-1,2-diethynyl olefins undergo cyclization to yield reactive 1,4-dehydrobenzenes; the products isolated may be derived from either unimolecular or bimolecular reactions of the intermediate. (Z)-4,5-Diethynyl-4-octene (4) undergoes rearrangement to yield 2,3-di-n-propyl-1,4-dehydrobenzene (17).Solution pyrolysis of 4 in inert aromatic solvent produces three unimolecular products, (Z)-dodeca-4,8-diyn-6-ene (7), benzocyclooctene (9), and o-allyl-n-propylbenzene (10), in high yield.When 1,4-cyclohexadiene is added to the pyrolysis solution as a trapping agent, high yields of the reduced product o-di-n-propylbenzene (12) are obtained.The kinetics of solution pyrolysis of 4 in the presence and absence of trapping agent establish that 2,3-di-n-propyl-1,4-dehydrobenzene is a discrete intermediate on the pathway leading to products.When the reaction was run in the heated probe of an NMR spectrometer, CIDNP was observed in 10.This observation, along with kinetic and chemical trapping evidence, indicates the presence of two additional intermediates, formed from 17 by squential intramolecular hydrogen transfer, on the pathway to products.The observation of CIDNP, coupled with the reactivity exhibited by 17 and the other two intermediates, implicates a biradical description of these molecules.Biradical 17 has been estimated to have a lifetime of about 10-9 s at 200 deg C and to lie in a well of about 5 kcal per mole with respect to the lowest energy unimolecular pathway ( hydrogen transfer).Ring opening (expected to be the lowest energy process for 1,4-dehydrobenzenes in which intramolecular hydrogen transfer is unlikely) to the isomeric diethynyl olefin 7 appears to have an activation enthalpy of about 10 kcal/mol.Upon thermal reaction in the gas phase (400 deg C) or in solution in inert solvents (Z)-2,3-diethylhexa-1,5-diyn-3-ene (5) rearranges in good yield to the isomeric diethynyl olefin (Z)-deca-3,7-diyn-5-ene (8) again presumably via 2,3-diethyl-1,4-dihydrobenzene 20 (addition of 1,4-cyclohexadiene to the reaction solution leads to a good yield of o-diethylbenzene, the expected trapping product of biradical 20).The absence of products due to intramolecular hydrogen transfer indicates that this process is at least 1 or 2 orders of magnitude slower than hydrogen transfer in 17.At 500 deg C in the gas phase products due to hydrogen transfer begin to appear.
