Charge‐Transfer‐Chromophore durch Cycloaddition‐Retro‐Elektrocyclisierung: multivalente Systeme und Kaskadenreaktionen

Kivala, Milan; Boudon, Corinne; Gisselbrecht, Jean‐Paul; Seiler, Paul; Gross, Maurice; Diederich, François

doi:10.1002/ange.200701733

Cited by 51 publications

(46 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…[10] NMR spectroscopy revealed the co-existence of different conformers at room temperature, which converged to a single species upon heating to 100 8C. In accordance to previous studies, [13] slow interconversion of similar dendralenes at room temperature is a consequence of steric crowding.…”

supporting

confidence: 83%

Cascade Pericyclic Reactions of Alleno‐Acetylenes: Facile Access to Highly Substituted Cyclobutene, Dendralene, Pentalene, and Indene Skeletons

Reisinger

Rivera‐Fuentes

Lampart

et al. 2011

Chemistry A European J

Self Cite

View full text Add to dashboard Cite

Cascade reactions are valuable tools for building complex molecular architectures with high efficiency, selectivity, and atom economy. These processes have a proven record in the preparation of natural products and biologically relevant molecules.[1] In a similar manner, cascade transformations would greatly benefit the field of advanced materials science, where they offer opportunities for rapid and divergent synthetic elaboration, thereby expanding the chemical space for functional materials.Allenes are particularly interesting candidates for the development of cascade reactions, given the diversity and specificity of their reaction modes.[2] Our interest in alleno-acetylenic scaffolding prompted us to introduce allenes as building blocks in the construction of three-dimensional chiral carbon-rich structures. To be able to prepare stable alleno-acetylenic chromophores, the 1,3-di-tert-butyl-1,3-diethynylallene (DEA) moiety was developed.[3] The introduction of tert-butyl substituents provides steric hindrance to the allene core, reducing its reactivity considerably. Taking advantage of the kinetic stability of these alleno-acetylenic scaffolds, we were able to resolve their enantiomers, [4] and use them to build enantiopure chiral push-pull chromophores, [4,5] macrocycles, [6] and helical foldamers. [7] Here, we explore the potential of the allene core of DEAs to participate in cascade pericyclic reactions, which lead to highly substituted complex carbon skeletons in a one-pot fashion, with excellent chemo-, regio-, and stereoselectivities. [8] We first investigated the reaction between racemic DEA (AE)-1 and 7,7,8,8-tetracyano-p-quinodimethane (TCNQ) and 1,1,2,2-tetracyanoethene (TCNE), to give butadienes (AE)-2 a and (AE)-2 b, respectively, by a formal [2 + 2] cycloaddition, followed by cycloreversion (CA/CR).[9] While the reaction with TCNE proceeded cleanly at room temperature, [4] we noticed that when the reaction with TCNQ was carried out at 40 8C, a significant amount of a by-product was formed. Isolation and characterization of this compound showed that adduct (AE)-2 a undergoes a 4p electrocyclization (EC) between the allene core and the proximal dicyanovinyl moiety, to give cyclobutene 3 a (Scheme 1). In a similar way, butadiene (AE)-2 b could be transformed into cyclobutene 3 b, in which water was eliminated from the acetonide protecting group. The molecular structures of cyclobutenes 3 a and 3 b were unambiguously assigned by X-ray diffraction studies (Scheme 1; for details, see the Supporting Information).[10]The triple CA/CR/EC cascade also produced dicyanocyclobutenes 18 and 19 (see Scheme SI1 in the Supporting Information) in high yield (82-87 %) with the acetonide protecting group replaced by an iPr 3 Si substituent. We found that addition of 10 equivalents of trifluoroacetic acid (TFA) accelerates the reaction and increases the yields significantly. It can be inferred that TFA protonates the aniline nitrogen, quenching the intramolecular charge-transfer interaction, and in turn making the dic...

show abstract

supporting

confidence: 83%

Cascade Pericyclic Reactions of Alleno‐Acetylenes: Facile Access to Highly Substituted Cyclobutene, Dendralene, Pentalene, and Indene Skeletons

Reisinger

Rivera‐Fuentes

Lampart

et al. 2011

Chemistry A European J

Self Cite

View full text Add to dashboard Cite

show abstract

“…Electrochemical investigations revealed that dendritic donor-substituted TCBDs undergo multiple redox steps at virtually matching potentials, [7] which suggests that the individual electron donor and acceptor moieties behave as independent electroactive centers. [12] This behavior has previously also been observed for ferrocenyl dendrimers by Astruc and co-workers [10] and by others.…”

Section: Resultsmentioning

confidence: 99%

“…[20] This is in very good agreement with the markedly lower first-oxidation potential of 7 (+ 0.41 V in CH 2 Cl 2 versus Fc + /Fc (ferricinium/ferrocene couple)) compared with 5 and 6 (+ 0.88 and + 0.89 V in CH 2 Cl 2 versus Fc + /Fc, respectively; see the Supporting Information). [7] The first-oxidation potential of 7, however, is considerably higher than that of 14, which is approximately À0.30 V in MeCN (versus Fc + /Fc) ( Figure 5). [21] Thus, a considerable interaction of the vinylogous tetrathiafulvalene-type donor with the 1,1,4,4-tetracyanobuta-1,3-dienyl moiety exists.…”

Section: Oxidation Of 2 With [Bis(trifluoroacetoxy)iodoa C H T U N G mentioning

confidence: 96%

“…[6,7] Compounds 4 and 6 were obtained in near-quantitative yield by efficient cycloaddition of TCNE with the corresponding alkyne precursors, followed by in situ retro-electrocyclization, as previously reported. In the synthesis of the dendritic systems 8 and 9, which feature a central triphenylamine core, sequences of iterative Sonogashira cross-couplings and silyl deprotections were applied.…”

Section: Synthesismentioning

confidence: 99%

See 1 more Smart Citation

One‐Electron‐Reduced and ‐Oxidized Stages of Donor‐Substituted 1,1,4,4‐Tetracyanobuta‐1,3‐dienes of Different Molecular Architectures

Kivala

Stanoeva²,

Michinobu

et al. 2008

Chemistry A European J

Self Cite

View full text Add to dashboard Cite

A series of monomeric and oligomeric donor-substituted 1,1,4,4-tetracyanobuta-1,3-dienes (TCBDs) with various topologies have been synthesized by means of thermal [2+2] cycloaddition between tetracyanoethylene (TCNE) and donor-substituted alkynes, followed by retro-electrocyclization. One-electron-reduced and -oxidized stages of the donor-substituted TCBDs were generated by chemical methods. The obtained radical anions and radical cations were studied by using electron paramagnetic resonance/electron nuclear double resonance (EPR/ENDOR) spectroscopy, supported by density functional theory (DFT) calculations. The extent of pi-electron delocalization in the paramagnetic species was investigated in terms of the EPR parameters. Despite favorable molecular orbital (MO) coefficients, the EPR results suggest that in radical anions the spin and charge are confined to the electron-withdrawing TCBD moieties on the hyperfine EPR timescale. The observed spin localization is presumably caused by an interplay between the nonplanarity of the studied pi systems, limited pi-electron conjugation, and very likely counterion effects. In radical cations, an analogous spin and charge localization confined to the electron-donating N,N-dialkylaniline moieties was found. In this case, an efficient electron delocalization is disabled by small MO coefficients at the joints between the donor and acceptor portions of the studied TCBDs.

show abstract

“…The protocol was adopted by several other groups using THF as a cosolvent with beneficial results [119]. Other common cosolvents include DMF [55,63], NMP (N-methylpyrrolidinone) [34,54,82,92], benzene [120], and toluene [62,78,121]. Although in many cases an increase in the solubility of catalysts, reactants, and products appeared to be a major factor [122], there is no detailed explanation for the observed reaction improvements due to solvent effects.…”

Section: Solvents and Additivesmentioning

confidence: 99%

Cross‐Coupling Reactions to sp Carbon Atoms

Schaub

Kivala

2013

Metal‐Catalyzed Cross‐Coupling Reactions and More

Self Cite

View full text Add to dashboard Cite

Charge‐Transfer‐Chromophore durch Cycloaddition‐Retro‐Elektrocyclisierung: multivalente Systeme und Kaskadenreaktionen

Cited by 51 publications

References 30 publications

Cascade Pericyclic Reactions of Alleno‐Acetylenes: Facile Access to Highly Substituted Cyclobutene, Dendralene, Pentalene, and Indene Skeletons

Cascade Pericyclic Reactions of Alleno‐Acetylenes: Facile Access to Highly Substituted Cyclobutene, Dendralene, Pentalene, and Indene Skeletons

One‐Electron‐Reduced and ‐Oxidized Stages of Donor‐Substituted 1,1,4,4‐Tetracyanobuta‐1,3‐dienes of Different Molecular Architectures

Cross‐Coupling Reactions to sp Carbon Atoms

Contact Info

Product

Resources

About