Oligoene‐Based π‐Helicenes or Dispiranes? Winding up Oligoyne Chains by a Multiple Carbopalladation/Stille/(Electrocyclization) Cascade

Milde, Bastian; Leibeling, Markus; Hecht, Alexander; Jones, Peter G.; Visscher, Arne; Stalke, Dietmar; Grunenberg, Jörg; Werz, Daniel B.

doi:10.1002/chem.201501797

Cited by 24 publications

(5 citation statements)

References 104 publications

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“…[37] Of tremendous variety and interest in and of themselves, helicenes also contain in their structures an all-Z, all-s-cis oligoene. Werz and coworkers [38,39] have reported the synthesis of a novel modification of the helicene framework, in which the π-system is truncated to just the all-Z oligoene chain of interest to us (exemplified here by 2). They call these remarkable molecules "helicenes truncated to a minimum".…”

Section: Resultsmentioning

confidence: 99%

Helical Oligoenes: Conformations, Bond Alternation, and Competing Through‐Bond and Through‐Space Transmission

Tsuji

Hoffmann

2016

Chemistry A European J

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There is a consensus that long-range electron transfer/transport occurs by a through-bond rather than through-space mechanism. In helical all-Z, all-s-cis oligoenes, one can set up an interesting competition in the medium-separation regime between a closer (in distance) through-space path and a more distant through-bond one. Although such oligoene conformations/isomers are unstable (by around 4 kcal mol(-1) per double bond relative to all-E, all-s-trans isomers), recent synthetic efforts on truncated helicenes and oligothiophenes have provided related molecules. On the way to transmission calculations with electrodes attached to the termini of helical oligoenes, we uncover an interesting conformational ambiguity in all-Z, all-s-cis oligoenes, the existence of a broad conformational minimum for helical compression, with hints of end-to-end frontier-orbital-caused stabilization. There is relationship between helical oligoene structures and the corresponding substructure of a helicene, but there are also significant differences in the number of olefin subunits per helix turn. In Hückel transport calculations, the role of TB or TS mechanisms is obscured to an extent by variations in bond alternation and dihedral angle along the oligomer chain. However, the operation of a dominant through bond mechanism emerges clearly in local transmission plots. In moving the electrodes to carbon position related by quantum interference, it is possible to uncover a through space mechanism.

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Section: Resultsmentioning

confidence: 99%

Helical Oligoenes: Conformations, Bond Alternation, and Competing Through‐Bond and Through‐Space Transmission

Tsuji

Hoffmann

2016

Chemistry A European J

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“…A spectacular Pd-catalyzed multiple domino reaction has been designed by Werz et al to construct complex scaffolds containing two five-membered oxacycles. 89 Precursors of type 147 have been involved in a process consisting of three consecutive cyclocarbopalladations (the first affording one oxacycle), followed by Stille cross-coupling and a final 6π-electrocyclization of the π-helicene intermediate 148 (Scheme 50). Oligoene-based dispiranes of type 149, variously substituted on the aromatic rings, have been obtained by this method in 50-85% yields.…”

Section: Scheme 49 Pd-catalyzed 5-exo-trig Cyclization Of Cyclohexadimentioning

confidence: 99%

Cyclocarbopalladation as a Key Step in Cascade Reactions: Recent Developments

et al. 2017

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Cascade reactions are step-economical processes for the synthesis of complex molecules as they allow, in one step, the formation of multiple bonds. Over the last two decades cyclocarbopalladation has emerged as a powerful key step when integrated into these sequences and has allowed unprecedented valuable polycyclic scaffolds to be obtained. This review is focused on recent developments in this field including original cascade sequences, novel activation modes (C-H activation for instance) and unprecedented families of substrates. 1 Introduction 2 Formation of Carbocycles 2.1 4-exo Cyclocarbopalladation 2.2 5-exo Cyclocarbopalladation 2.3 5-endo Cyclocarbopalladation 2.4 Cyclocarbopalladation with Formation of Six-Membered Carbocycles 2.5 Cyclocarbopalladation with Formation of Seven-Membered Carbocycles 3 Formation of Heterocycles 3.1 Formation of Nitrogen Heterocycles 3.2 Formation of Oxygen Heterocycles 3.3 Formation of Sulfur Heterocycles 3.4 Formation of Silicon-Containing Heterocycles 4 Conclusion

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“…Helicene-like molecules, that is, polycyclic aromatic compounds with nonplanar screw-shaped scaffolds, have been receiving increasing attention due to their unique structure characterized by helicity and their unusual physicochemical properties like second-order nonlinear optical (NLO) properties, two-photon circular dichroism, , circularly polarized luminescence, and so on. Recent rapid advances in synthetic technology have realized a variety of molecules with helical scaffolds, ,− and investigations of exploring their mechanisms as well as of materials design are intensively conducted toward the realization of future photonics devices based on such helicene-like molecules.…”

Section: Introductionmentioning

confidence: 99%

Theoretical Study on Second Hyperpolarizabilities of Intramolecular Pancake-Bonded Diradicaloids with Helical Scaffolds

Takamuku¹,

Nakano

2019

ACS Omega

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Using the spin-unrestricted density functional theory method, we have investigated a novel class of open-shell singlet fused-ring molecules with helical scaffolds toward the development of highly efficient third-order nonlinear optical (NLO) systems. It turns out that the helical molecules possess pancake bonding with intermediate diradical character and thereby exhibit large enhancement of orientationally-averaged second hyperpolarizability γ s values (third-order NLO properties at the molecular scale) as compared to their closed-shell analogues. It is also found that the asymmetric charge distribution between the cofacial radical sites located on both the terminal rings of the helical scaffold leads to further enhancement of the γ value in the intermediate open-shell character region as compared to the open-shell analogues without asymmetric charge distributions. These results indicate that the helical systems with intermediate diradical character are potential candidates for the building block of highly efficient openshell singlet NLO materials, which are superior to the conventional closed-shell NLO materials.

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Oligoene‐Based π‐Helicenes or Dispiranes? Winding up Oligoyne Chains by a Multiple Carbopalladation/Stille/(Electrocyclization) Cascade

Cited by 24 publications

References 104 publications

Helical Oligoenes: Conformations, Bond Alternation, and Competing Through‐Bond and Through‐Space Transmission

Helical Oligoenes: Conformations, Bond Alternation, and Competing Through‐Bond and Through‐Space Transmission

Cyclocarbopalladation as a Key Step in Cascade Reactions: Recent Developments

Theoretical Study on Second Hyperpolarizabilities of Intramolecular Pancake-Bonded Diradicaloids with Helical Scaffolds

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