Helicene-like chiral auxiliaries in asymmetric catalysis

Aillard, Paul; Voituriez, Arnaud; Marinetti, Angéla

doi:10.1039/c4dt01935k

Cited by 160 publications

(257 citation statements)

References 75 publications

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“…Since various helicene-based phosphine-related ligands have been reviewed [2,5,[7][8][9], only recent selected examples capable of delivering exceptionally high ee values are summarized here.…”

Section: Helicenes As Chiral Catalystsmentioning

confidence: 99%

“…Thus, chromatographically separated endo-76 effectively catalyzes the enantioselective cycloisomerization of N-tethered 1,6-enyne 78 to give bicyclo[4.1.0]heptane 79 with 95% yield and 81% ee, whilst exo-77 remained almost inactive [56] (Scheme 12). Meanwhile, various phosphole-containing ligands were also prepared and screened in similar reactions with success [8,9,57]. Scheme 11.…”

Section: Scheme 11mentioning

confidence: 99%

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Helicene-Based Chiral Auxiliaries and Chirogenesis

Hasan

Borovkov

2017

Symmetry

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Helicenes are unique helical chromophores possessing advanced and well-controlled spectral and chemical properties owing to their diverse functionalization and defined structures. Specific modification of these molecules by introducing aromatic rings of differing nature and different functional groups results in special chiroptical properties, making them effective chiral auxiliaries and supramolecular chirogenic hosts. This review aims to highlight these distinct structural features of helicenes; the different synthetic and supramolecular approaches responsible for their efficient chirality control; and their employment in the chirogenic systems, which are still not fully explored. It further covers the limitation, scope, and future prospects of helicene chromophores in chiral chemistry.

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Section: Helicenes As Chiral Catalystsmentioning

confidence: 99%

Section: Scheme 11mentioning

confidence: 99%

Helicene-Based Chiral Auxiliaries and Chirogenesis

Hasan

Borovkov

2017

Symmetry

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“…Thus, helicenes can be utilized them a broad range of applications in chiral materials, in the chiral recognition of biomolecules, and in asymmetric synthesis161718192021222324. More specifically, chiral helicene-based trivalent phosphorus ligands are efficient asymmetric inductors in metal-catalyzed asymmetric reactions and show good to excellent enantioselectivities252627282930313233.…”

mentioning

confidence: 99%

Rational Design and Synthesis of [5]Helicene-Derived Phosphine Ligands and Their Application in Pd-Catalyzed Asymmetric Reactions

Yamamoto

Shimizu

Igawa

et al. 2016

Sci Rep

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A series of novel optically active [5]helicene-derived phosphine ligands (L1, with a 7,8-dihydro[5]helicene core structure- and L2, with a fully aromatic [5]helicene core structure) were synthesized. Despite their structural similarities, L1 and L2 exhibit particularly different characteristics in their use as chiral ligands. L1 was highly effective in the asymmetric allylation of indoles with 1,3-diphenylallyl acetate (up to 99% ee), and in the etherification of alcohols (up to 96% ee). In contrast, L2 was highly effective in the stereocontrol of helical chirality in Suzuki–Miyaura coupling (SMC) reaction (up to 99% ee). Density functional theory analysis was employed to propose a model that accounts for the origin of the enantioselectivity in these reactions.

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“…Helicenes are polycyclic aromatic compounds with screw-shaped skeletons formed by ortho-fused benzene or other aromatic rings. asymmetric catalysis, [18][19][20][21] liquid crystal molecules, 22 enantioselective fluorescent sensors, 23 rotors, 24 nonlinear optics, 25-27 molecular recognition [28][29][30][31] and organic electronics [32][33][34][35][36] ). As a consequence, helicenes exhibit high optical rotation and circular dichroism values in the visible region.…”

Section: Introductionmentioning

confidence: 99%

Photophysical properties of quinoxaline-fused [7]carbohelicene derivatives

Liu

Pan

et al. 2015

RSC Adv.

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Helicene and its derivatives have received much attention as the candidates of organic photoelectronic material. Recently, novel quinoxaline-fused [7]carbohelicene derivatives exhibit unique structural and photophysical properties, especially in the crystal states. However, their structure-property relationships have not been fully understood from the micromechanism, which is also important to further improve their performance. Here, the electronic transition, electronic circular dichroism (CD), second-order nonlinear optical (NLO) response and charge transport properties of five quinoxaline-fused [7]carbohelicene derivatives have been investigated based on density functional theory calculations. The experimental UV-Vis/CD spectra of the studied compounds were well reproduced by our calculations. Thus, we can assign their electron transition properties and absolution configurations (ACs) with high confidence. It is found that CD bands of quinoxaline-fused [7]carbohelicene derivatives mainly originate from exciton coupling between quinoxaline, phenyl or 4-methoxyphenyl and [7]carbohelicene, which is in sharp contrast to [7]carbohelicene. More interestingly, these derivatives possess large first hyperpolarizability values. For example, the βHRS value of compound 6 is 32.96 × 10 −30 esu, which is about 190 times larger than that of the organic urea molecule. The bandwidth of valence band of compound 2 is comparable to that of conduction band and slightly larger than that of tris(8-hydroxyquinolinato)aluminium. This means that compound 2 is the potential candidate as ambipolar charge transport material. Please do not adjust marginsPlease do not adjust margins modulates the LUMO energy level. As a consequence, LUMO energy of compound 2 is much lower than that of compound 1 (Table S6), which leads to the smaller energy gap (Eg) for compound 2. Moreover, the main electron transitions characters are of charge transfer from quinoxaline to [7]carbohelicene and vice versa (Fig. 3). On the basis of above analysis, it is found that involvement of quinoxaline unit not only modulates the electron absorption wavelength but also alter the electron transition property. Compounds 3 and 4 also exhibit four absorption bands, which is similar to those of compound 2. In other words, the substituent effect of phenyl or 4-methoxyphenyl group on the UV-Vis spectra of compound 2 is not great. It is noted that some of the molecular orbitals involved in these transitions partially located on the phenyl or 4-methoxyphenyl group. Fig. 2Calculated UV-Vis (left) and CD (right) spectra in gas phase of 1, 2, 3 and 4 at the TDB3LYP/6-31+G(d) level of theory along with the experimental spectra (red dashed line).

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Helicene-like chiral auxiliaries in asymmetric catalysis

Cited by 160 publications

References 75 publications

Helicene-Based Chiral Auxiliaries and Chirogenesis

Helicene-Based Chiral Auxiliaries and Chirogenesis

Rational Design and Synthesis of [5]Helicene-Derived Phosphine Ligands and Their Application in Pd-Catalyzed Asymmetric Reactions

Photophysical properties of quinoxaline-fused [7]carbohelicene derivatives

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