Thermolabile Kohlenwasserstoffe, XIX. Synthesen, Spektren, Struktur und Spannung hochverzweigter Pentane

Hellmann, S.; Beckhaus, Hans‐Dieter; Rüchardt, Christoph

doi:10.1002/cber.19831160614

Cited by 22 publications

(8 citation statements)

References 37 publications

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“…The solvent was removed by distillation over a small Vigreux column, and 2,3,4,4-tetramethylpent-1-ene (7; 98 mg, 78%) was distilled from a microflask at 120 -1238. The 1 H-and 13 C-NMR spectra are in full agreement with those described by Rüchardt and co-workers [25] for a specimen of 7 which was obtained from 2,2,4,4-tetramethylpentan-3-ol with HMPT (3 h, 2208) [26]. The parameters of the 1 H-NMR spectrum showed unidentified signals at 0.9 -1.9 ppm, less than 5%; the only 13 C-NMR signals of olefinic C-atoms were those of 7.…”

Section: Methodssupporting

confidence: 86%

Reactions of Di(tert‐butyl)diazomethane with Acceptor‐Substituted Ethylenes

Huisgen

Pöchlauer

Mlostoń

et al. 2007

Helvetica Chimica Acta

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Dedicated to Herbert Mayr on the occasion of his 60th birthday Di(tert-butyl)diazomethane (4) is a nucleophilic 1,3-dipole with strong steric hindrance at one terminus. In its reaction with 2,3-bis(trifluoromethyl)fumaronitrile ((E)-BTE), a highly electrophilic tetra-acceptor-substituted ethene, an imino-substituted cyclopentene 9 is formed as a 1 : 2 product. The open-chain zwitterion 10, assumed as intermediate, adds the second molecule of (E)-BTE. The 19 F-and 13 C-NMR spectra allow the structural assignment of two diastereoisomers, 9A and 9B. The zwitterion 10 can also be intercepted by dimethyl 2,3-dicyanofumarate (11) and furnishes diastereoisomeric cyclopentenes 12A and 12B; an X-ray-analysis of 12B confirms the mixed 1 : 1 : 1 product. Competing is an (E)-BTE-catalyzed decomposition of 4 to give 2,3,4,4-tetramethylpent-1-ene (7) þ N 2 ; the reaction of (E)-BTE with a trace of water appears to be responsible for the chain initiation. The H 2 SO 4 -catalyzed decomposition of diazoalkane 4, indeed, produced the alkene 7 in high yield. The attack on the hindered diazoalkane 4 by 11 is slower than that by (E)-BTE; the zwitterionic intermediate 21 undergoes cyclization and furnishes the tetrasubstituted furan 22. In fumaronitrile, electrophilicity and steric demand are diminished, and a 1,3-cycloaddition produces the 4,5-dihydro-1H-pyrazole derivative 25. The reaction of 4 with dimethyl acetylenedicarboxylate leads to pyrazole 29 þ isobutene. Methyl diazoacetate (1) is a 1,3-dipole with well-balanced nucleophilicity and electrophilicity; i.e., 1 undergoes cycloadditions with electrophilic (a,b-unsaturated carbonyl compounds and nitriles) and nucleophilic dipolarophiles (enamines, ynamines) [1] [6]. Whereas dimethyl diazomalonate (2) and methyl diazo(phenylsulfonyl)acetate (3) move towards electrophilic 1,3-dipoles on the continuous scale [6], diazomethane, higher diazoalkanes, and phenylated diazomethanes are nucleophilic

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Section: Methodssupporting

confidence: 86%

Reactions of Di(tert‐butyl)diazomethane with Acceptor‐Substituted Ethylenes

Huisgen

Pöchlauer

Mlostoń

et al. 2007

Helvetica Chimica Acta

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“…Compounds 2 c, [17] 3 b, [44] 3 c, [16] 5 c, [45] 6 d, [46] 10, [47] 11, [21] 12, [48] and 13 [49] were prepared by published methods.…”

Section: Methodsmentioning

confidence: 99%

Reactions of Aliphatic Ketones R2CO (R=Me, Et,iPr, andtBu) with the MCl4/Li(Hg) System (M=U or Ti): Mechanistic Analogies between the McMurry, Wittig, and Clemmensen Reactions

Villiers

Ephritikhine

2001

Chem. Eur. J.

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Analysis of the products of the reactions of ketones R2CO (R = Me, Et, iPr, tBu) with the MCl4/Li(Hg) system (M = U, Ti) at 20 degrees C revealed significant differences. For R = Me, the reaction proceeded exclusively (M = U) or preferentially (M = Ti) via a metallopinacol intermediate resulting from dimerization of ketyl radicals. Pinacol was liberated by hydrolysis, and tetramethylethylene was obtained after further reduction at 65 degrees C. For R=iPr, formation of iPr2C=CiPr2 as the only coupling product, the nonproduction of this alkene by reduction of the uranium pinacolate [U]-OCR2CR2O-[U] (R= iPr) at 20 degrees C, and the instability of the corresponding titanium pinacolate towards rupture of the pinacolic C-C bond indicated that reductive coupling of iPr2CO did not proceed by dimerization of ketyl radicals. Formation of 2,4-dimethyl-2-pentene was in favor of a carbenoid intermediate resulting from deoxygenative reduction of the ketyl. These results revealed that for sterically hindered ketones, McMurry reactions can be viewed as Wittig-like olefination reactions. For R=tBu, no coupling product was obtained and the alkane tBu2CH2 was the major product. The involvement of the carbenoid species [M]=CtBu2 was confirmed by its trapping with H2O, leading to tBu2CH2, and with the aldehydes RCHO, giving the cross-coupling products tBu2C=C(R)H (R = Me, tBu). Therefore, in the case of severely congested ketones, McMurry reactions present strong similarities to the Clemmensen reduction of ketones, owing to the involvement in both reactions of carbenoid species which exhibit similar reactivity.

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“…L group includes all six compounds, whose PMR spectra we have (2200, 3200, 3300, 4200, 4300, 4400). [7] the studied spectra of the hydrogen atom signals were not found.…”

Section: 1 Quasi-linear Alkanes (Code: 4n 2 00)mentioning

confidence: 88%

“…As stated above, we used only the spectral parameters δ Н , published in the chemical literature [3,4,7,8].We present these data (including above comments done) separately for each of the 5 above described fragments, composing each of the 4 branches of the considered spherical alkanes. We selected the order of consideration of these fragments as follows.…”

Section: IImentioning

confidence: 99%

Peculiar properties of «spherical» pentanes 1H NMR Spectra. <span> </span>

Mizyuk

Shybanov

Karpyak

2016

Proceedings of the 20th International Electronic Conference on Synthetic Organic Chemistry

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Abstract. We propose the concept of the spherical (or «ball-shaped») compounds. In this communication we are considered NMR 1 H spectra of 53 «spherical pentanes» -saturated hydrocarbons with a maximum length of the chain of five carbon atoms [from simplest n-pentane to most complicated tetra-(tert-butyl)methane]. The conception of the spherical alkane structure includes: a) a central carbon atom of the whole molecule (С 3 ); b) two, three or four carboncontaining branches attached to it. These include monocarbonic methyl (Me) and dicarbonic (longest chain) Et, Pr i , Bu t -fragments; c) one or two branches may be the hydrogen atoms. The central atom (С 3 ) is surrounded by three layers, called: a) inner -α-layer, b) intermediate -β-layer, and c) the outer -γ-layer, which is often referred to -ω-layer. The inner and intermediate layers may contain both carbon and hydrogen atoms, but the outer layer contain only hydrogen atoms. We consider several types of alkanes sphericity: «quasi-spherical», «minimally-spherical», and «maximally-spherical», as well as linear (n-pentane) and «quasi-linear». The values of proton chemical shifts in spherical alkanes depend on the location of the studied hydrogen atoms in a certain layer. The number of hydrogen atoms in the outer ω-layer (H ω ) and the uniformity of their distribution in the volume of this outer layer (which depends on the type of alkane sphericity) have a significant influence on the proton chemical shifts. When parameter H ω = 12 (or 15) we observe the maximal upfield signals shift of all studied protons (except the methyne hydrogens of isopropyl group). With further growth of H ω an increase of the chemical shifts (downfield shift) observed. When H ω = 12 (or 15) for the methyl groups of ethyl fragments in the maximally-spherical compounds observed the highest upfield shift. The same applies to methylene groups of ethyl fragments.To explain these results, the hypothesis, assuming the interaction to each other of three (or especially four) carboncontaining branches, radiating from the central carbon atom С 3 in spherical molecules proposed. This interaction, in our opinion, causes the observable upfield shift of the methyl, methylene or methyne proton's signals and is similar to the proposed earlier interaction of two or three heteroatoms in the case of «anomeric effect» in CHXYZ compounds with gemlocation of heteroatoms X, Y, Z.Key words: «spherical («ball-shaped») pentanes»; central carbon atom of molecule (С 3 ); carboncontaining branches; ω-layer; types of alkanes sphericity: «quasi-spherical», «minimally-spherical», and «maximally-spherical», number of hydrogen atoms in the outer ω-layer (H ω ).2

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Thermolabile Kohlenwasserstoffe, XIX. Synthesen, Spektren, Struktur und Spannung hochverzweigter Pentane

Abstract: Die Synthesen und spektroskopischen Eigenschaften von acht Kohlenwasserstoffen R1R2CHC(CH3)3 (3a–h) und zehn Kohlenwasserstoffen R1R2R3C  C(CH3)3 (4a‐k) (R = Alkyl) werden beschrieben und die Strukturen und Spannungsenthalpien anhand von Kraftfeldrechnungen diskutiert.

Cited by 22 publications

References 37 publications

Reactions of Di(tert‐butyl)diazomethane with Acceptor‐Substituted Ethylenes

Reactions of Di(tert‐butyl)diazomethane with Acceptor‐Substituted Ethylenes

Reactions of Aliphatic Ketones R2CO (R=Me, Et,iPr, andtBu) with the MCl4/Li(Hg) System (M=U or Ti): Mechanistic Analogies between the McMurry, Wittig, and Clemmensen Reactions

Peculiar properties of «spherical» pentanes 1H NMR Spectra. <span> </span>

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Thermolabile Kohlenwasserstoffe, XIX. Synthesen, Spektren, Struktur und Spannung hochverzweigter Pentane

Abstract: Die Synthesen und spektroskopischen Eigenschaften von acht Kohlenwasserstoffen R1R2CHC(CH3)3 (3a–h) und zehn Kohlenwasserstoffen R1R2R3C  C(CH3)3 (4a‐k) (R = Alkyl) werden beschrieben und die Strukturen und Spannungsenthalpien anhand von Kraftfeldrechnungen diskutiert.

Cited by 22 publications

References 37 publications

Reactions of Di(tert‐butyl)diazomethane with Acceptor‐Substituted Ethylenes

Reactions of Di(tert‐butyl)diazomethane with Acceptor‐Substituted Ethylenes

Reactions of Aliphatic Ketones R2CO (R=Me, Et,iPr, andtBu) with the MCl4/Li(Hg) System (M=U or Ti): Mechanistic Analogies between the McMurry, Wittig, and Clemmensen Reactions

Peculiar properties of &laquo;spherical&raquo; pentanes 1H NMR Spectra. <span> </span>

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Peculiar properties of «spherical» pentanes 1H NMR Spectra. <span> </span>