A convenient procedure for the synthesis of tetrathia-[7]-helicene and the selective α-functionalisation of terminal thiophene ring

Maiorana, Stefano; Papagni, Antonio; Licandro, Emanuela; Annunziata, Rita; Paravidino, Piero; Perdicchia, Dario; Giannini, Clelia; Bencini, Marco; Clays, Koen; Persoons, André

doi:10.1016/s0040-4020(03)01056-1

Cited by 83 publications

(56 citation statements)

References 26 publications

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“…[2a] Tetrathiaheterohelicene (7-TH) 1a has an extended conjugated π system, and a configurationally stable helix with intrinsic asymmetry, which can be separated into M and P enantiomers. Furthermore, we have established that the 7-TH system can be easily functionalized at the alpha positions of the two terminal thiophene rings, [3] allowing the modulation of the chemical and physical properties by varying the substituents. In addition, the presence of substituents with different steric demands can tune the distance between the two terminal thiophene rings resulting in remarkable variations in the dihedral angle of the molecule, which can accommodate Special Section a variety of bulky groups at C2 and C13.…”

Section: Introductionmentioning

confidence: 99%

Tetrathiaheterohelicene Phosphanes as Helical‐Shaped Chiral Ligands for Catalysis

Monteforte¹,

Cauteruccio²,

Maiorana³

et al. 2011

Eur J Org Chem

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Tetrathia[7]helicene-based phosphanes thiaheliphos (2a), nPr-thiaheliphos (2b) and di-nPr-thiaheliphos (2c) have been prepared from the 2,13-dilithio derivatives of thiahelicenes 1a–c by reaction with an excess of Ph2PCl. Protection of the air-sensitive products as BH3 adducts, from which the phosphanes 2a–c are easily regenerated on heating with ethanol, is described. New rhodium(I) complexes 8 and 9 were obtained by reaction of 2c with [Rh(COD)2]+[BF4]– and [BARF]–, respectively, which were converted by oxidation into the chelating phosphane–phosphane oxide RhI complexes 10 and 11. The monophosphane 5 was similarly prepared, andreaction of the dilithio species with ClP(O)(OEt)2 gave the diphosphonate 17, which was characterized by X-ray crystallography. Comparison of data from DFT calculations (B3LYP/SVP) on 2c, 8 and 10 and X-ray data for 17 reveals a strong tension within the thiaheliphos ligands that is partially relaxed by increasing the Rh–P distances and the bite angle of the chelating ligand. Compound (P)-(+)-1c, obtained by chromatographic resolution, was transformed into optically pure (P)-(+)-2c, which was used in the asymmetric hydrogenation of itaconic acid ester and methyl 2-acetamidoacrylate (product ees up to 40%)

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Section: Introductionmentioning

confidence: 99%

Tetrathiaheterohelicene Phosphanes as Helical‐Shaped Chiral Ligands for Catalysis

Monteforte¹,

Cauteruccio²,

Maiorana³

et al. 2011

Eur J Org Chem

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“…[13]helicene from hexahelicene-2-carboxylic acid) [49]. The oxidative photocycliza tion of stilbenes is still the method of choice for the preparation of selected [n]helicenes and their heteroatom analogs [50][51][52][53][54][55][56][57][58].…”

Section: Photochemical Synthesesmentioning

confidence: 99%

Synthesis and Characterization of Novel Chiral Conjugated Materials

Rajca

Miyasaka

2006

Functional Organic Materials

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“…[19] With respect to NPP, in helicenes, the p-conjugated segment is the helix itself, which opens up the way to enhanced nonlinear responses. This result has rapidly inspired many experimental [20][21][22] and theoretical [23][24][25][26] studies on helicenes, with a view to optimizing their second-order NLO responses. For [N]-helicenes, time-dependent Hartree-Fock (TDHF)/Austin Model 1 (AM1) simulations predict that the antisymmetric isotropic component of the first hyperpolarizability [b(À3w;2w,w)] increases monotonically with the size of the helix.…”

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confidence: 97%

“…[26] Hetero-helicenes have also been investigated and in particular tetrathia- [7]-helicene and its substituted analogs. [27] Reference [22] describes a convenient preparation of tetrathia- [7]-helicene and its 2-formylsubstituted species, whereas near-resonance hyper-Rayleigh scattering (HRS) experiments are described in ref. [21].…”

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Theoretical Design of Substituted Tetrathia‐[7]‐Helicenes with Large Second‐Order Nonlinear Optical Responses

et al. 2004

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Second-order nonlinear optical (NLO) materials have attracted a lot of interest because of foreseeable applications in optoelectronic technology.[1] In particular, organic compounds are attractive for this purpose because of their large and fast responses combined with the flexibility of organic synthesis which hastens the design of new chromophores. The first generation of NLO organic chromophores consists of one-dimensional (1D) p-conjugated systems end-capped with donor (D) and acceptor (A) moieties. Experimental and theoretical work has shown during the last decades how to choose the D/A strengths and p segments for optimizing the second-order NLO responses.[2-4] Later, two-dimensional (2D) octupolar molecules such as 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) were shown to exhibit second-order NLO responses that can be as large as those of their dipolar analogues. [5][6][7] In addition, with these 2D structures, some of the limitations of the 1D dipolar structures were displaced, if not overcome. Indeed, 1D compounds suffer from the transparency-efficiency tradeoff, which is difficult to achieve because the desirable increase in b(the first hyperpolarizability) is accompanied by a bathochromatic shift of the electronic transitions. Moreover, their dipolar nature and the predominance of dipole-dipole intermolecular interactions favor the formation of centrosymmetric crystal arrangements which exhibit no second harmonic generation (SHG) responses. In addition, phase-matching conditions cause only a fraction of the microscopic response to be preserved at the macroscopic scale.[8] On the other hand, octupolar compounds present an improved nonlinearity/transparency tradeoff, enable non-centrosymmetric crystal structures owing to their lack of permanent dipole moment, and present large offdiagonal b tensor components that can give rise to large macroscopic SHG responses. [6] [a] Dr.

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A convenient procedure for the synthesis of tetrathia-[7]-helicene and the selective α-functionalisation of terminal thiophene ring

Cited by 83 publications

References 26 publications

Tetrathiaheterohelicene Phosphanes as Helical‐Shaped Chiral Ligands for Catalysis

Tetrathiaheterohelicene Phosphanes as Helical‐Shaped Chiral Ligands for Catalysis

Synthesis and Characterization of Novel Chiral Conjugated Materials

Theoretical Design of Substituted Tetrathia‐[7]‐Helicenes with Large Second‐Order Nonlinear Optical Responses

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