Ein einfacher Weg zu<i>trans</i>-3,4-Dihalocyclobuten

Hoberg, Heinz; Fröhlich, Christian

doi:10.1055/s-1981-29618

Cited by 20 publications

(15 citation statements)

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“…Assignments of subbands in the P branch were less cer- tain due to the strength and abundance of lines in this region from the 826 cm À1 band of the trans,trans species. Predictions from R-branch assignments and GSCDs led to reasonable assignments for subbands from P P 6 to P P 16 . A total of 758 lines was assigned, and 323 GSCDs were derived from this band.…”

Section: Butadiene-cistrans-14-dmentioning

confidence: 84%

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Rotational analysis of bands in the high-resolution infrared spectra of the three species of butadiene-1,4-d2; refinement of the assignments of the vibrational fundamentals

Craig

Hanson

Pierce

et al. 2004

Journal of Molecular Spectroscopy

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Section: Butadiene-cistrans-14-dmentioning

confidence: 84%

“…trans-3,4-Dichlorocyclobutene was prepared by anhydrous (Aldrich) Al 2 Cl 6 -catalyzed isomerization of cis-1,4-dichlorocyclobutene (Fluka) [16,17]. ttDClBDE was prepared by stereospecific isomerization of trans-3,4-dichlorocyclobutene heated in a glass bulb at 86°C for 3 h [18].…”

Section: Synthesismentioning

confidence: 99%

Rotational analysis of bands in the high-resolution infrared spectra of the three species of butadiene-1,4-d2; refinement of the assignments of the vibrational fundamentals

Craig

Hanson

Pierce

et al. 2004

Journal of Molecular Spectroscopy

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“…Decarboxylation to l b was carried out according to the method of Wove & Campbell [19]. The same sequence applied to 5a which is available by treatment of 5 with AlCl, [20] afforded la. Pyrolysis of 5a to 6a occurred in 1 h at 90" [20] [21].…”

Section: Synthesis Of Cis-and Tvuns-(36-d)-14-~yclohexadiene (La) mentioning

confidence: 99%

“…The same sequence applied to 5a which is available by treatment of 5 with AlCl, [20] afforded la. Pyrolysis of 5a to 6a occurred in 1 h at 90" [20] [21]. After reduction to 7a as described above, 'H-and 2H-NMR spectra showed the presence of 20-30% contamination with the ( Z , E)-and/or (E, E)-isomers but again exact sample composition could not be determined.…”

Section: Synthesis Of Cis-and Tvuns-(36-d)-14-~yclohexadiene (La) mentioning

confidence: 99%

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Stereochemistry of Dehydrogenation of 1,4,‐Cyclohexadiene with 2,3‐Dichloro‐5,6‐dicyano‐p‐benzoquinone

Müller

Joly

Mermoud

1984

Helvetica Chimica Acta

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Summarycis-and trans-(3,6-D2)-1 ,Ccyclohexadienes l a and l b have been synthesized from cis-3,4-dichlorocyclobutene (5). Aromatization to benzene with DDQ is cis-stereospecific with an uncertainty of 5 % . This result is discussed in relation to concerted or stepwise mechanisms for aromatization of 1,4-dihydroaromatics with 2,3-dichloro-5,6-dicyano-p -benzoquinone (DDQ).Introduction. -Oxidation of hydrocarbons with quinones proceeds via hydride transfer from the substrate to the quinone (mechanism A , Scheme 1) [l]. In agreement with this description, reaction rates of substituted toluenes with 2,3-dichIoro-5,6-dicyano-p-benzoquinone (DDQ) correlate with o giving a p-value of -4.3 [2]. Accordingly, substrates capable of forming stable carbenium ions upon hydride transfer exhibit enhanced reactivity. For example, cycloheptatriene reacts 200 times faster than 1,3-cycloheptadiene, and 1,2,3-triphenylcyclopropene ca. lo5 times faster than triphenylmethane [3] [4]. Similarly, vicinal dehydrogenation is believed to proceed in a stepwise manner (mechanism B ) involving sequential hydride and proton loss [5]. The partial cis-stereospecificity observed for dehydrogenation of acenaphthene has been ascribed to formation of an ion pair as reactive intermediate [6]. In contrast, dehydrogenation of 1 ,Ccyclohexadiene (1) and its benzannulated homologues does not fit this mechanistic picture. The reactivity of these compounds is usually about 100 times higher than that of 1,2-dihydroaromatics or similar model compounds, and it approaches that of cycloheptatrienes, provided that loss of two H-atoms from the allylic positions is possible [3-51. The enhanced rate of 1,6dihydroaromatics can be understood if it is assumed that part of the aromatic stabilization of the product is already reflected in the transition state of the reaction. This mechanistic hypothesis requires concerted loss of two H-atoms from the I,Cpositions, either in a cyclic mechanism (C) involving two cis-H-atoms, or in a cis-or trans-conjugate 1,Celimination (D). The cyclic mechanism C was proposed by Stoos & R o h k , when they found that cis-3,6-dimethyl-1 ,Ccyclohexadiene (2) reacts ca. 20 times faster than the trans-isomer 3 and 700 times faster than the 3,3-dimethyl derivative 4 [4]. Although the preference for cis-

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The Thermally and Photochemically Induced Ring Opening ofcis-3,4-Dichlorocyclobutene andtrans-3,4-Dichlorocyclobutene: New Insights from a Matrix-Spectroscopic Study

Maier¹,

Bothur

1998

Eur. J. Org. Chem.

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Ein einfacher Weg zutrans-3,4-Dihalocyclobuten

Cited by 20 publications

References 0 publications

Rotational analysis of bands in the high-resolution infrared spectra of the three species of butadiene-1,4-d2; refinement of the assignments of the vibrational fundamentals

Rotational analysis of bands in the high-resolution infrared spectra of the three species of butadiene-1,4-d2; refinement of the assignments of the vibrational fundamentals

Stereochemistry of Dehydrogenation of 1,4,‐Cyclohexadiene with 2,3‐Dichloro‐5,6‐dicyano‐p‐benzoquinone

The Thermally and Photochemically Induced Ring Opening ofcis-3,4-Dichlorocyclobutene andtrans-3,4-Dichlorocyclobutene: New Insights from a Matrix-Spectroscopic Study

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