Cycloadditions of substituted 1,2‐dimethylenecyclopentanes. — The influence of methyl groups on the rate of diels‐alder reactions

Sustmann, Reiner; Daute, P.; Sauer, Ralf; Sommer, Angelika; Trahanovsky, Walter S.

doi:10.1002/cber.19891220827

Cited by 9 publications

(1 citation statement)

References 22 publications

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“…By combining the information from the NMR and mass spectra, pyrolysis product 47 was identified (Table 5). Pyrolysis (27), 41 (11).…”

Section: -(Acetozymethyl)-2-[l-(trimethylsilyl)ethyl]furan (16)mentioning

confidence: 99%

Dimerization kinetics and products of. alpha. -substituted o-quinodimethanes derived from benzene and furan

Leung¹

1992

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Leung, Man-kit, "Dimerization kinetics and products of [alpha]-substituted o-quinodimethanes derived from benzene and furan " (1991 INFORMATION TO USERSThis manuscript has been reproduced from the microfihn master. UMI films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from any type of computer printer.The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adversely affect reproduction.In the unlikely event that the author did not send UMI a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion.Oversize materials (e.g., maps, drawings, charts) are reproduced by sectioning the original, beginning at the upper left-hand corner and continuing from left to right in equal sections with small overlaps. Each original is also photographed in one exposure and is included in reduced form at the back of the book.Photographs included in the original manuscript have been reproduced xerographically in this copy. Higher quality 6" x 9" black and white photographic prints are available for any photographs or illustrations appearing in this copy for an additional charge. Contact UMI directly to order. Signature was redacted for privacy.Signature was redacted for privacy.Signature was redacted for privacy. ^H NMR spectrum (300 MHz, CDCI3) of the [4+2] dlmer 33 of 3-ethylldene-2-methylene-2,3-dlhydrofuran (12) (s: chloroform and one furan proton of the dlmer, w: HgO, H; high boiling residue from hexanes, the eluent). 64Figure A-7. ^H NMR spectrum (300 MHz, CDCI3) of the [4+2] dimer 34 of 3-ethylIdene-2-methylene-2,3-dihydrofuran (12) (s: c hloroform and one furan proton of the dlmer, w; HgO, H: high boiling residue from hexanes, the eluent). 65Figure A-8. ^H NMR spectrum (300 MHz, CDCI3) of the pyrolysate of the [4+21 dimer 34 of 3-ethylldene-2-methylene-2,3-dlhydrofuran (12) (s; chloroform, w: HgO, H: high boiling residue from hexanes, the eluent). 66Figure A-9. ^H NMR spectrum (300 MHz, CDCI3) of the Dlels-Alder adducts (28) of methyl acrylate and 3-ethylldene-2-methylene-2,3-dihydrofuran (12). 67Figure A-10. Gas chromatograph ( DBl, temperature program, 80 °C (5 min), 5 °C/min, 200 °C) of the Dlels-Alder adducts (28) of methyl acrylate and 3-ethylldene-2-methylene-2,3-dihydrofuran (12) (A: Dlels-Alder adducts). 68Figure A-11. ^H NMR spectrum (300 MHz, CDCI3) of the dlmer mixture of 2-ethylldene-3-methylene-2,3-dIhydrofuran (13). 69Figure A-12. Gas chromatograph (DBl,temperature program, 60 °C, 5 mIn, 2 °C/mln 180°C) of the dlmer mixture of 2-ethylidene-3-methylene-2,3-dIhydrofuran (13) (D: dlmer). NMR spectrum (300 MHz, CDCI3) of the [4+4] dimer 38 71 of 2-ethylidene-3-methylene-2,3-dihydrofuran (13) (s: chloroform, w: HgO, H: high boilin...

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“…By combining the information from the NMR and mass spectra, pyrolysis product 47 was identified (Table 5). Pyrolysis (27), 41 (11).…”

Section: -(Acetozymethyl)-2-[l-(trimethylsilyl)ethyl]furan (16)mentioning

confidence: 99%

Dimerization kinetics and products of. alpha. -substituted o-quinodimethanes derived from benzene and furan

Leung¹

1992

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FMO Approach in [4 + 2] Cycloadditions. Kinetic Studies with 1,2‐Dimethylenecyclopentane

Sustmann

Siangouri‐Feulner

1993

Chem. Ber.

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Kinetic measurements on [4 + 21 cycloadditions of 1,a-dimethylenecyclopentane (1) as a model diene for normal DielsAlder reactions are described. This diene was selected in order to check whether a synperiplanar diene is a good test case for the FMO model. Using HOMO and LUMO energies from semiempirical quantumchemical calculations, we indeed obtained a good linear correlation between the lg k2 values and l/(EHomo -ELUMO). The cycloadditions of E / Z isomeric dienophiles to 1 are stereospecific. These reactions are best described in terms of concerted processes.The frontier molecular orbital (FMO) theory is the most widely accepted approach to explain reactivity in [4 + 21 cycloadditiens [',*]. While it works satisfactorily on a qualitative basis, most attempts to apply it quantitatively to Diels-Alder reactions have proved unsuccessful. Thus, rather poor quantitative correlations between Ig k2 and the first ionization potentials as a measure of the HOMO energy of the diene were obtained for cycloadditions of substituted 1,3-butadienes to maleic anhydride or tetracyanoethylener3I. A better agreement between this simplified theory and experiments was found for the classic cycloadditions of cyclopentadiene to cyano-substituted 01efins [~]. Rather poor correlations resulted for cycloadditions of substituted anthracenes to maleic anhydridet5], whereas in other examples better correlations were reportedI6I. In 1,3-dipolar cycloadditions, the other important class of [x4 + x2] cycloadditions a much better agreement between this theory and experiments is There are several reasons for the shortcomings in the FMO approach. It derives from the second-order perturbation theory and reduces the full expression for the stabilizing electronic interaction, which includes all occupied and unoccupied MOs of the reactants, to those of the frontier orbitals [']. Although these contributions should be greater than those from the interactions of other unoccupied with occupied MOs there is no a priori postulate that such a theory will work in explaining quantitatively reactivity in cycloadditions. On the contrary, it is surprising that the FMO theory functions as good as it does"'].Furthermore, the second-order perturbation theory describes only stabilizing electronic interactions. Thus, steric effects which are known to be important in many cases are not considered. More elaborate perturbation theories["] do take into account these contributions and constitute, therefore, an improvement. However, also these treatments rely on the quality of the underlying semiempirical SCF procedures like MNDO, AM1, or In the case of Diels-Alder reactions of open-chain dienes the position of the equilibrium between the synperiplanar and antiperplanar structure, i. e. a conformational situation, is another complicating factor. It is mainly influenced by the number and the size of substituents at different positions of the diene. This complex situation was present in the kinetic study of the cycloadditions of substituted 1,3-butadienes to maleic anhydr...

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Cycloadditions, 43^[1]. Cyclobutanones via Photoreactions of Chromium‐Carbene Complexes with Olefins and Dienes – A Comparison with the Traditional Ketene Method

1993

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Photolysis of chromium-carbene complexes 1 in the presence of olefins and dienes yields cyclobutanones 4 and 5 with varying stereoselectivity. Under oxidative conditions lactones 6,7, 8, and 10 are obtained as byproducts. Thermal reactions of ketenes 3 with olefins and dienes yield the same cyclobutanones with usually equal selectivities. In the case of 2,3-dihydro-1,4-dioxin as olefin, diene 9 is obtained as a byproduct. Cycloaddition reactions of 1 a or 3a with 1,2-dimethylenecyclopentane (11) yield the spirocyclic cyclobutanones 12 and 13.The symmetric ketone 16 and the ketene dimer 17 are formed as additional products upon cycloaddition of ketene 3 b to tetraethoxyethylene. Novel a-(buty1thio)cyclobutanones 4 j, k, 1, m and 5k, 1 are formed by cycloaddition reactions of the newly In contrast to methoxy(methy1)ketene (3a) cycloadditicyl reactions of methyl(pheny1thio)ketene (3 b) are well-Chem.

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Cycloadditions of substituted 1,2‐dimethylenecyclopentanes. — The influence of methyl groups on the rate of diels‐alder reactions

Cited by 9 publications

References 22 publications

Dimerization kinetics and products of. alpha. -substituted o-quinodimethanes derived from benzene and furan

Dimerization kinetics and products of. alpha. -substituted o-quinodimethanes derived from benzene and furan

FMO Approach in [4 + 2] Cycloadditions. Kinetic Studies with 1,2‐Dimethylenecyclopentane

Cycloadditions, 43^[1]. Cyclobutanones via Photoreactions of Chromium‐Carbene Complexes with Olefins and Dienes – A Comparison with the Traditional Ketene Method

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Cycloadditions of substituted 1,2‐dimethylenecyclopentanes. — The influence of methyl groups on the rate of diels‐alder reactions

Cited by 9 publications

References 22 publications

Dimerization kinetics and products of. alpha. -substituted o-quinodimethanes derived from benzene and furan

Dimerization kinetics and products of. alpha. -substituted o-quinodimethanes derived from benzene and furan

FMO Approach in [4 + 2] Cycloadditions. Kinetic Studies with 1,2‐Dimethylenecyclopentane

Cycloadditions, 43[1]. Cyclobutanones via Photoreactions of Chromium‐Carbene Complexes with Olefins and Dienes – A Comparison with the Traditional Ketene Method

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Cycloadditions, 43^[1]. Cyclobutanones via Photoreactions of Chromium‐Carbene Complexes with Olefins and Dienes – A Comparison with the Traditional Ketene Method