Synthesis and resolution of 2-(diphenylphosphino)heptahelicene

Abed, Riadh El; Aloui, Faouzi; Genêt, Jean‐Pierre; Hassine, Béchir Ben; Marinetti, Angéla

doi:10.1016/j.jorganchem.2006.11.022

Cited by 58 publications

(27 citation statements)

References 24 publications

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“…The same year, these groups reported the synthesis and resolution of 2-(diphenylphosphino)heptahelicene 403. 370 In this case, the diphenylphosphine oxide group was introduced at the early stage of the synthesis and it was shown that oxidative photocyclization was compatible with the presence of such function (Scheme 97). Finally, the phosphine oxide 402 was reduced to phosphine 403 using HSiCl 3 /NEt 3 .…”

Section: Carbo[7]helicene Phosphanesmentioning

confidence: 99%

Enantioenriched Helicenes and Helicenoids Containing Main-Group Elements (B, Si, N, P)

2019

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In this review, we discuss the rich chemistry of helicenes and helicenoids containing maingroup elements. Enantioenriched helicenic derivatives containing main-group elements B, Si, N and P, either incorporated within the helical backbone or grafted to it, will be thoroughly presented. We will describe their synthesis, resolution, and asymmetric synthesis, their structural features, electronic and chiroptical properties, emission, together with other photochemical properties and applications. OUTLINE 14 The absorption spectrum of 19c recorded in CH 2 Cl 2 solutions exhibited a maximum at 376 nm which is significantly red shifted compared with that of double [5]helicene 19a (310 nm) due to the more extended π-conjugation in 19c. According to TD-DFT calculations, the low-energy absorption band from 400 to 500 nm is assignable to the HOMO→LUMO transition corresponding to a π−π* transition of the fully conjugated bis-helical system. DFT calculations revealed a very high theoretical isomerization barrier of 45.1 kcal/mol for the (P,P)/(M,M)-19c stereoisomer, i.e. 4.4 kcal/mol higher than the (P,M) stereoisomer (not observed experimentally). The high configurational stability of 19c enabled to obtain the pure (P,P)and (M,M)-19c by chiral HPLC (Daicel Chiralcel IE column; EtOAc/MeOH = 9:1 as eluent) and to study their chiroptical properties. The ECD spectrum of (P,P)-19c in CH 2 Cl 2 displayed two strong positive bands at 275 and 320 nm, a strong negative one at 375 nm and a broad and less intense one between 425-475 nm. 52 Note that the isomerization barrier of the OBO-fused double [7]helicene is much higher than for oxabora[6]helicene 9 (vide supra) and higher than carbo[7]helicene (42.0 kcal/ mol), indicating the advantage of double helicenes over monohelicenes in terms of conformational stability. Indeed no racemization was observed upon heating enantiomer (P,P) and (M,M)-19c for 24 h up to 200 °C. 52 Note that in 2017 a longer double OBO-helicene analogue was deposited on a Au(111) under UHV conditions and its surface-assisted cyclodehydrogenation into a planar OBO-perihexacene was observed by STM. 54 Similarly to 6 and 9, the strong bond alternation found in the BOC4 rings of 19a 51 may account for the small NICS value of 1.3 while the surrounding C6 rings, including the distorted central benzene ring, show large negative NICS values (Scheme 3c). For comparison, in the all-carbon analogue tetrabenzo-[a,f,j,o]perylene shown in Scheme 3c, the central C6 ring shows a positive NICS value, indicating substantial antiaromatic character. Notably, molecular orbital calculations of 19a indicate that the HOMO and LUMO are spread over the C6 rings rather than on the boron and oxygen atoms, accounting for the substantial stability of 19a (Scheme 3c). Borahelicenes are efficient blue fluorophores. Indeed, azabora[6]helicene 6 displays blue fluorescence at 447 nm (Table 2), while smaller achiral [4]helicenic systems were successfully used as host materials in phosphorescent OLEDs with efficiencies better than the classical 4,4'...

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Section: Carbo[7]helicene Phosphanesmentioning

confidence: 99%

Enantioenriched Helicenes and Helicenoids Containing Main-Group Elements (B, Si, N, P)

2019

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“…For example, structures 7 [17], 8 [18], and 9 [19] are all [5]helicenes, but not [6]helicenes, despite the presence of six aromatic rings in total ( Figure 2). The functionalized helicenes such as 10 [20], 11 [21], and 12 [22] (Figure 2) which have a heteroatom as a substituent on the aromatic ring, as in the case of amino, hydroxyl (phenolic or alcoholic), thiol, or phosphorus-containing groups, are still carbohelicenes but not heterohelicenes. In order to specify the position of functional group(s), a numbering system is used, as shown in the structure 10.…”

Section: Carbohelicenesmentioning

confidence: 99%

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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“…A first class includes compounds displaying a phosphorus group attached to a helicene-like scaffold. Notably, Ru (II), 9,10 Rh(I), 11 Pd (II), 9,[12][13][14] Cu(I), 15,16 and Au(I) 17,18 complexes of these phosphines have been prepared and fully characterized. The second class is made of phosphahelicenes that is helicenes with a phosphorus ring embedded into the helical scaffold itself.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and X‐ray diffraction study of a chiral bis‐phosphahelicene palladium (II) complex

et al. 2019

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As a complement to our previous studies on the development of a class of chiral phosphahelicenes, this article discloses the synthesis, spectroscopic, and structural characterizations of a new phosphahelicene transition metal complex. It demonstrates the ability of these hindered chiral ligands to coordinate Pd (II) in trans‐complexes Cl2Pd(L*)2. In the solid state, the complex adopts a C2‐symmetric arrangement with two ligands facing each other on the same face of the coordination plane. X‐Ray data highlight bending of the Pd (II) unit from the expected planar coordination geometry that might be due to a significant π‐π stacking effect between the central rings of two helical units.

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Synthesis and resolution of 2-(diphenylphosphino)heptahelicene

Cited by 58 publications

References 24 publications

Enantioenriched Helicenes and Helicenoids Containing Main-Group Elements (B, Si, N, P)

Enantioenriched Helicenes and Helicenoids Containing Main-Group Elements (B, Si, N, P)

Helicene-Based Chiral Auxiliaries and Chirogenesis

Synthesis and X‐ray diffraction study of a chiral bis‐phosphahelicene palladium (II) complex

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