“Push‐Pull” Substituted Allenes

Saalfrank, Rolf W.

doi:10.1002/ijch.198500091

Cited by 21 publications

(10 citation statements)

References 100 publications

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“…As a result of the poor solubility of 3 at room temperature, 13 C NMR characterization was performed at 50 °C in [D 6 ]benzene. The relative position of the signals for the central and terminal allenic carbon atoms of 3 ( δ =110.2 and 144.8 ppm, respectively) are the reverse of that observed for nonpolarized allenes ( δ =185–215 and 60–130 ppm, respectively),13b but similar to that reported for tetrakis(dimethylamino)allene ( δ =136 and 162 ppm, respectively) 14a. This difference is indicative of the strong polarization of the π system, but not indicative of a bent structure (see below).…”

Section: Methodssupporting

confidence: 75%

Synthesis of an Extremely Bent Acyclic Allene (A “Carbodicarbene”): A Strong Donor Ligand

et al. 2008

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Bis ans Limit: Werden CC‐π‐Bindungen durch Push‐push‐Substitution aufs Äußerste gespannt, so entstehen gebogene Allene (siehe Struktur; C türkis, N blau). In einem acyclischen Allen beträgt der CCC‐Bindungswinkel nur noch 134.8°; das üblicherweise sp‐hybridisierte zentrale Kohlenstoffatom nähert sich daher einer Konfiguration mit zwei freien Elektronenpaaren an und wirkt als sehr starker η1‐Donorligand für Übergangsmetallzentren.

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Section: Methodssupporting

confidence: 75%

Synthesis of an Extremely Bent Acyclic Allene (A “Carbodicarbene”): A Strong Donor Ligand

et al. 2008

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“…Such a scenario might be enhanced by incorporating electron-donating and -withdrawing substituents at the termini, and "push-pull" allenes of this type have been comprehensively reviewed by Saalfrank [25]. However, thus far there is no compelling evidence that the carbene-like structure is a predominant resonance contributor.…”

Section: Ferrocenyl-allenesmentioning

confidence: 99%

From allenes to tetracenes: Syntheses, structures, and reactivity of the intermediates

Banide

Oulié

McGlinchey

2009

Pure and Applied Chemistry

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Each step of the conversion of a series of 9-alkynyl-9H-fluorenes into the corresponding fluorenylidene-allenes that dimerize and proceed sequentially via head-to-tail and tail-to-tail dialkylidene-cyclobutanes, en route to electroluminescent tetracenes, has been characterized X-ray crystallographically. Allenes possessing substituents of very different electronic and steric character, such as aryl, halogeno, silyl, phosphino, and ferrocenyl, exhibit novel and unexpected reactivity patterns. The silyl-allenes dimerize to yield 1,2-bis(fluorenylidene)cyclobutanes of intrinsic C 2 symmetry as a result of the overlapping fluorenylidenes with their large wingspans. Thermal rearrangement of a bis(fluorenyl)bis(trimethylsilyl)-diallene generates the tetrabenzo-quatercyclopentadiene, C 60 H 36 , which represents 60 % of the C 60 framework. An attempt to isolate a "push-pull" allene, whose central carbon possesses carbene character, was made by incorporating a cation-stabilizing substituent (ferrocenyl) and an aromatic anionic moiety (fluorenide) at the termini. However, the allene underwent facile dimerization to the very heavily congested 3,4-di(spirofluorenyl)-1,2-bis(ferrocenyl-chloromethylene)cyclobutane that exhibits a very long (1.65 Å) C(3)-C(4) bond. Extension of this chemistry to dibenzosuberenylidene-allenes led to a straightforward route to the hitherto difficultly available dibenz[c,d,h]azulene system. Moreover, the reaction of 5-phenylethynyl-5H-dibenzo[a,d]cyclohepten-5-ol with dicobalt octacarbonyl yielded, surprisingly, the first isolated example of a (µ-alkyne)Co 2 (CO) 5 (η 2 -alkene)complex, the long-sought first intermediate in the proposed mechanism of the Pauson-Khand reaction (PKR).

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“…Furthermore, allenes of type 22 are able to perform carbene-like reactions. 27,28 The two prototype push-pull substituted allenes (cyclopropenylidene)(cyclopentadienylidene) methane 23 and (cyclopentadienylidene)(cycloheptatrienylidene) methane 24 remain unknown. 29 Although (fluoren-9-ylidene)(dibenzo[a,d]cyclohepten-5-ylidene)methane 25 has been synthesized, its spectroscopic data indicate no significant carbene character 30 (Scheme 9).…”

Section: Push-pull Substituted Allenesmentioning

confidence: 99%

“…Subsequently, the intermediate s-(Z), a,b-(Z) and s-(Z) pentadienones undergo an electrocyclic reaction that is analogous to the hexatriene-cyclohexadiene rearrangement to give the dimers 31. 27,28,33,34,36 The diethoxy pyranes 31 are converted to the corresponding a-pyrones 32 on refluxing in glacial acetic acid. These compounds are strongly fluorescent and particularly well suited as laser dyes because of their exceptional stability 37 (Scheme 10).…”

Section: Push-pull Substituted Allenesmentioning

confidence: 99%

Roots: From carbenes to allenes and coordination polymers : Ever present never twice the same

Saalfrank

Maid

2005

Chem. Commun.

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The purpose of this Feature Article is to demonstrate that recognizing the similarities in different areas of chemistry allows the prediction of potential results in related fields. For instance, during our investigations of 2,2-diethoxyvinylidene-triphenylphosphorane we became interested in 2,2-diethoxydiazoethene. In order to obtain diazoethenes, we studied vinyl-diazonium salts and geminal vinyl-diazides as precursors. In the course of these investigations, we realized their synthetic potential to produce, via substituent-dependent 1,5-, 3,5-, or 1,5'-cyclization, a whole variety of heterocycles. However, more importantly, we became familiar with the chemistry of carbenes, which prompted an investigation of the carbene-like character of push-pull substituted allenes. Due to the ambiphilicity of their central carbon atom, they readily dimerized. Consequently, our strong interests in push-pull substituted allenes drew our attention to tetradonor substituted allenes, and as a result, we employed tetraethoxyallene as a synthetic equivalent to the fictitious malonic ester 1,1-/1,3-dianion synthon. This concept led to the synthesis of heterocumulenes and to the transallenation reaction to give allenecarboxanilides, which was further developed as a cumuhomologation for the synthesis of butatrienes via haloallenes from propargyl alcohols. The Diels-Alder reaction and intramolecular domino cyclization of multi-functional allenecarboxanilides yielded complex fused heteroarenes. Finally, the 1,5-cyclization of vinyl-azides, reported earlier, provided tetrazolylidene ligands, triggering our interest in supramolecular coordination chemistry, for example, the synthesis of one-, two- and three-dimensional coordination polymers.

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“Push‐Pull” Substituted Allenes

Cited by 21 publications

References 100 publications

Synthesis of an Extremely Bent Acyclic Allene (A “Carbodicarbene”): A Strong Donor Ligand

Synthesis of an Extremely Bent Acyclic Allene (A “Carbodicarbene”): A Strong Donor Ligand

From allenes to tetracenes: Syntheses, structures, and reactivity of the intermediates

Roots: From carbenes to allenes and coordination polymers : Ever present never twice the same

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