Benzyne, cyclohexyne, and 3-azacyclohexyne and the problem of cycloalkyne versus cycloalkylideneketene genesis

Wentrup, Curt; Blanch, Rodney J.; Briehl, Horst; Groß, Gerhard

doi:10.1021/ja00214a034

Cited by 167 publications

(117 citation statements)

References 3 publications

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“…Just as in the case of the lower homolog, matrix isolation has allowed recording of the IR spectrum of 56 (Scheme 7.12) [53,54].…”

Section: Cyclohexyne and Its Derivativesmentioning

confidence: 99%

Angle‐Strained Cycloalkynes

Hopf¹,

Grunenberg²

2009

Strained Hydrocarbons

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IntroductionAccording to the sp-hybridization model, the carbon-carbon triple bond possesses a linear structure, and indeed, many alkynes fulfill this prediction. High level ab initio calculations [1] of isolated alkyne molecules, as well as gas phase electron diffraction experiments [2] reveal their linear minimum structure. On the other hand, given that the C C-R bending force constant becomes intrinsically smaller for substituted alkynes and polyynes, crystal packing effects may lead to deviations from strictly linear geometries [3]. From a dynamic point of view even in the case of acetylene one has to include the -albeit reduced -flexibility of the carboncarbon triple bond in order to describe, for example, the vinylidene acetylene rearrangement (see below) [4]. Further, the linear sp-hybrid picture only holds true for the electronic ground state. Cis-and trans-bent configurations are known in the case of low-lying electronic states [5]. Nevertheless, many alkynes correspond to the prediction of linearity due to the sp-hybrid model, and we have collected a selection of typical examples, reaching from the parent compound acetylene 1 via a few alkyl 2-4 and aryl acetylenes 5-7 to a functionalized acetylene, dimethyl acetylenedicarboxylate 8, in Scheme 7.1, together with the appropriate references [1, 2, 6-11], all dating from the recent literature.The easiest way to distort a triple bond is to incorporate it into a sufficiently small ring structure. The question, of course, is what this ring size is, and from what ring size on the respective cycloalkynes can we isolate compounds, that can be worked with under normal laboratory conditions [12]. Rather than using the nonspecific term 'distorted cycloalkyne' Krebs [12] prefers to speak of 'angle-strained cycloalkynes'. Since it is easier to deform a C C-C arrangement than its more hydrogenated olefinic and saturated analogs, relatively large angle deformations are possible in cycloalkynes without significant changes in energy. Krebs arbitrarily considers all cycloalkynes in which the C C-C angle is deformed by more than 10° as angle-strained [12]. Accepting this definition, the stable cyclononyne (see below) is an angle-strained cycloalkyne, whereas cyclodecyne is not.

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“…Just as in the case of the lower homolog, matrix isolation has allowed recording of the IR spectrum of 56 (Scheme 7.12) [53,54].…”

Section: Cyclohexyne and Its Derivativesmentioning

confidence: 99%

Angle‐Strained Cycloalkynes

Hopf¹,

Grunenberg²

2009

Strained Hydrocarbons

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“…Solomon, and Wentrup and coworkers 85 have recently observed and isolated quinone methide 31 at low temperature by flash vacuum pyrolysis 86,87 (FVP) of 27, which was sublimed at ca 45…”

Section: Ortho-quinone Methidementioning

confidence: 99%

Polymers Based on Phenols

Solomon¹,

Qiao²,

Caulfield³

2003

PATAI'S Chemistry of Functional Groups

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“…Matrix isolation was carried out using 10 cm long, 0.8 cm diameter quartz tube in an oven dircctly attached to the vacuum shroud of a Leyhold-Heraeus o r Air Products liquid Hc cryostat [37]. Argon, nitrogen, and xcnon were used as matrix media, which werc passed over the sample while it was subliming, and co-condensed as a matrix at ca.…”

Section: Experimental and Computational Proceduresmentioning

confidence: 99%

The Vinylketene‐Acylallene Rearrangement: Theory and Experiment

Bibas¹,

Wong²,

Wentrup³

1997

Chemistry A European J

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Alkoxyvinylketenes4are generated by flash vacuum thermolysis (FVT) or photolysis of 3-alkoxycyclobutenones3. The thermal interconversion of4and allene carboxylic acid esters5under FVT conditions is demonstrated by Ar matrix FTIR spectroscopy. In addition, ethoxy-vinylketene4bundergoes thermal elimination of ethene with formation ofs-cis-ands-trans-acetylketene(8). An analogous aminovinylketene-to-allenecarbox-amide conversion is observed on FVT of 3-dimethylaminocyclobutenone3c. A facile 1, 3-chlorine migration in 2, 3-buta-dienoyl chloride(5d)is also reported. Consistent with the experimental observations, 1, 3-methoxy, 1, 3-chloro, and 1, 3-dimethylamino migrations in vinylketene are calculated (G2(MP2, SVP) level) to have moderate barriers of 169, 157, and 129 kJ mol(-1) , respectively, significantly less than the corresponding 1, 3-H shift barrier (273 kJ mol(-1) ). The stabilization of the four-center transition structures is rationalized in terms of the donor-acceptor interaction between the lone pair electrons of the migrating donor substituent and the vacant central carbon p orbital of the ketene LUMO. The predicted migratory aptitude in the series of substituted vinylketenes, R-C(CH2 )-CHCO, is in the order N(CH3 )2 >SCH3 >SH>Cl>NH2 >OCH3 >OH>F>H>CH3 , and correlates well with the electron-donating ability of the R group.

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Benzyne, cyclohexyne, and 3-azacyclohexyne and the problem of cycloalkyne versus cycloalkylideneketene genesis

Cited by 167 publications

References 3 publications

Angle‐Strained Cycloalkynes

Angle‐Strained Cycloalkynes

Polymers Based on Phenols

The Vinylketene‐Acylallene Rearrangement: Theory and Experiment

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