A non-photochemical route to synthesize simple benzo[1,2-b:4,3-b′]dithiophenes: FeCl<sub>3</sub>-mediated cyclization of dithienyl ethenes

Cauteruccio, Silvia; Dova, D.; Graiff, Claudia; Carrara, C.; Doulcet, Julien; Stephenson, G. R.; Licandro, Emanuela

doi:10.1039/c3nj01567j

Cited by 8 publications

(22 citation statements)

References 43 publications

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“…The products were evaluated with 7,8-dipropyltetrathia [7]helicene (5)i nastandard KR procedure (Scheme1,T able2). Despite relativelyl ow enantioselectivities, early results ( Ta ble 2, 4a-f)g ave us important clues and it quickly became clear that chiral scaffolds that were prized in asymmetric deprotonation (4a, 4d), [15] and organocatalysis (4b, 4c [16] and 4g [17] )g ave poor results when modified for use in asymmetricf ormylation.…”

Section: Resultsmentioning

confidence: 99%

“…As ar esult of the work described here, previously unexplored chiral formamidesa re now readily available, providing an important range of structurally varied new chiral auxiliaries. The practicality of enantioselective formylation has been established for the first time as ak inetic resolution procedure with (rac)-7,8-dipropyltetrathia [7]helicene, and we have identified ap referentials ubstitution pattern (R 1 = iPr,R 2 = Me, R 3 = H, R 4 = aryl) surrounding the N-formyl centre, with R 4 = naphthyl (4j) and pyrenyl (4q)g iving the best results, affording (M)-2formyl-7,8-dipropyltetrathia [7]helicene (6)r espectively in 30 % and 32 %y ields, and 40 %a nd 42 % ee from the single-KR version of the reaction. This process has been appliedi naonepot double-KR which gave improved ee values (68-73 %) and established practical access to optically pure helicenes by this method.…”

Section: Discussionmentioning

confidence: 99%

“…This process has been appliedi naonepot double-KR which gave improved ee values (68-73 %) and established practical access to optically pure helicenes by this method. As new generationso fc hiral formyl donors become availablet he final crystallisation to achieve enantiomeric purity will be far more efficient when startingf or ah igheri nitial ee The 2,13-diformyl-7,8-dipropyltetrathia [7]helicene (7)o btained using double-KR offers an excellent buildingb lock for the construction of innovative (A)-(chiral p)-(A) NLO-phores which con-form to the novel and recently reported 'double-dipole halfturn' design. [5] Experimental Section…”

Section: Discussionmentioning

confidence: 99%

“…[1] There are manyc lasseso ff unctional C 2 -symmetric (rac)-arenes and heteroarenes such biaryls, paracyclophanes, helicenes and also metallocenes where chiral formyl donors could provide au seful strategy for access to enantiopure samples,a nd in this paper we reporto ur first-generation results to develop the methodology as an approachf or the kinetic resolution of helicenes. Helicenes, in particular,have been the subjectofi ntense research in the past decade, [2] but despite many efforts to access enantiomerically pure helicenes, and some noteable individual successes, [3] there is still no generally applicablea pproach.O ur interesti nt etrathia [7]helicenes as bidentate ligands, [4] or as powerful chiral NLO-responsive chromophores (NLOphores), [5] which required an easy method to prepare enantiopure 2-formyl-or 2,13-diformyltetrathia [7]helicenes, [6] led us to investigate an ovel approachb ased on asymmetric formylation.…”

Section: Introductionmentioning

confidence: 99%

“…We report the preparation and evaluation of 23 chiralf ormamides (20 synthesised for the first time for this project)i nt he kinetic resolution (KR) of 7,8-dipropyltetrathia [7]helicene (5) which was chosenb ecause of its ease of preparation, [7] and because of the availability of efficient methods to perform lithiation at the 2-position. [8] Furthermore, conventional formylation of 2-lithio-tetrathia [7]helicenes with DMF is widely used in the racemic series. [6] This paper,h owever,d escribes the first examples of the chiralm odification of this well-knownr eaction.…”

Section: Introductionmentioning

confidence: 99%

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Novel Asymmetric Formylation of Aromatic Compounds: Enantioselective Synthesis of Formyl 7,8‐Dipropyltetrathia[7]helicenes

Doulcet

Stephenson

2015

Chemistry A European J

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Asymmetric formylation of aromatic compounds is virtually unexplored. We report the synthesis and evaluation of a library including 20 new chiral formamides in the kinetic resolution of 7,8-dipropyltetrathia[7]helicene, affording the corresponding formyl- or diformylhelicenes in up to 73 % ee, making enantiopure compounds available by recrystallisation. With the N,N-disubstituted formamides used in this study, the best enantioselectivity has been achieved with R(1) =iPr, R(2) =Me, R(3) =H, R(4) =1-naphthyl or its 1-pyrenyl equivalent.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Novel Asymmetric Formylation of Aromatic Compounds: Enantioselective Synthesis of Formyl 7,8‐Dipropyltetrathia[7]helicenes

Doulcet

Stephenson

2015

Chemistry A European J

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Benzodithienyl Silanes for Organic Electronics: AIE Solid‐State Blue Emitters and High Triplet Energy Charge‐Transport Materials

Bossi¹,

Arnaboldi

Castellano

et al. 2020

Advanced Optical Materials

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the design and preparation of organic semiconducting frameworks and the thoroughly understanding of the structureproperty-function correlations. Advanced microscopic techniques were lately employed to deepen the comprehension of the solid-state supramolecular organization, intermolecular interactions, and interfacial phenomena linked to material processing. [3,4] This is the case of OLEDs which, given their potential to achieve 100% electron to photon conversion efficiency, are the reference technology employed in energy saving flat panel displays and promising alternative to develop solid-state lighting. OLEDs, in their simplest configuration, are composed of a stack of different organic or organometallic semiconducting materials layered, with appropriate techniques, between two electrodes. The electroluminescence (EL) process, leading to light emission, is the result of recombination into the emitting layer of the charges, holes and electrons, injected from the transparent anode and the metal cathode. The charge recombination produces excitons which, trapped by the emissive material, radiatively decay with the emission of photons. The emissive layer (EML) is typically a dispersion of phosphorescent transition-metal complex emitters, mostly based on Ir(III) and Pt(II) metal ions, into an organic host material. [5−8] In recent years, a new paradigm emerged in OLED technology that is the use of pure organic compounds as dopant able to harvest, similarly to the transition-metal complexes, both singlet and triplet electrogenerated excitons, through the so called thermally activated delayed fluorescence (TADF). [9] In either cases, phosphorescent or TADF-OLEDs, the host material has to meet a complex profile of requirements, including: i) triplet excitation energy exceeding that of the emitter; ii) frontier energy orbitals matching those of the neighbor layers in order to trap charges (both electrons and holes) and transfer the excitation energy to the emitter; iii) stability under device operation; iv) ability to form an amorphous stable phase with good morphology; v) ease of large scale synthesis. [10−15] Extended π-conjugated fused aromatic molecules fit almost all the mentioned requirements due to their rigid π skeletons, A novel class of benzo[1,2-b:4,3-b′]dithienyl (BDT) silanes 1-3 in which a tetrahedral silicon atom connects two BDT units is developed as high triplet energy 3D-host. The photophysical and electrochemical properties of these structures are investigated, demonstrating that the peculiar features of the constituting BDT units are preserved in the corresponding silanes. All compounds display deep UV absorption (E g = 4.10-3.52 eV) and fluorescent emission (300-400 nm for 1 and 2, and 350-450 nm for 3). Phosphorescence is observed at low temperature and the respective T 1 states set at 2.65, 2.59, and 2.25 eV. Emission efficiency in solution is as high as 0.18 in 3. Compound 1 crystallizes in two monoclinic structures without relevant intrainter-molecular contacts; both display similar and intriguin...

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The Use of (−)‐Sparteine/Organolithium Reagents for the Enantioselective Lithiation of 7,8‐Dipropyltetrathia[7]helicene: Single and Double Kinetic Resolution Procedures

Doulcet

Stephenson

2015

Chemistry A European J

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The effect of organolithium reagent (RLi: R=nBu, iPr, sBu, tBu), solvent (diethyl ether, diethyl ether/THF and MTBE), and stoichiometry on the (-)-sparteine-mediated silylation of 7,8-dipropyltetrathia[7]helicene shows that, unusually, substantially more than 0.5 equivalent of RLi (R=iPr, sBu, tBu) and a large excess of (-)-sparteine (R=nBu, sBu) is often needed to achieve substantial conversions and good ee values. With nBuLi, however, just one equivalent of the organolithium reagent is sufficient to obtain high conversions. Our best results were obtained using the convenient tBuLi/(-)-sparteine adduct with which the need for a high (-)-sparteine/RLi ratio can be avoided. Single- and double-kinetic resolution (KR) procedures give enantiopure samples of 2-trimethylsilyl- and 2,13-di(trimethylsilyl)-7,8-dipropyltetrathia[7]helicene and two-step double-KR combining (-)-sparteine/sBuLi and chiral formamides affords the synthetically valuable 2-formyl-7,8-dipropyltetrathia[7]helicene. This is the first use of (-)-sparteine for the enantioselective lithiation of helicenes and the first report of tBuLi outperforming sBuLi in a (-)-sparteine-mediated procedure.

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A non-photochemical route to synthesize simple benzo[1,2-b:4,3-b′]dithiophenes: FeCl₃-mediated cyclization of dithienyl ethenes

Cited by 8 publications

References 43 publications

Novel Asymmetric Formylation of Aromatic Compounds: Enantioselective Synthesis of Formyl 7,8‐Dipropyltetrathia[7]helicenes

Novel Asymmetric Formylation of Aromatic Compounds: Enantioselective Synthesis of Formyl 7,8‐Dipropyltetrathia[7]helicenes

Benzodithienyl Silanes for Organic Electronics: AIE Solid‐State Blue Emitters and High Triplet Energy Charge‐Transport Materials

The Use of (−)‐Sparteine/Organolithium Reagents for the Enantioselective Lithiation of 7,8‐Dipropyltetrathia[7]helicene: Single and Double Kinetic Resolution Procedures

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A non-photochemical route to synthesize simple benzo[1,2-b:4,3-b′]dithiophenes: FeCl3-mediated cyclization of dithienyl ethenes

Cited by 8 publications

References 43 publications

Novel Asymmetric Formylation of Aromatic Compounds: Enantioselective Synthesis of Formyl 7,8‐Dipropyltetrathia[7]helicenes

Novel Asymmetric Formylation of Aromatic Compounds: Enantioselective Synthesis of Formyl 7,8‐Dipropyltetrathia[7]helicenes

Benzodithienyl Silanes for Organic Electronics: AIE Solid‐State Blue Emitters and High Triplet Energy Charge‐Transport Materials

The Use of (−)‐Sparteine/Organolithium Reagents for the Enantioselective Lithiation of 7,8‐Dipropyltetrathia[7]helicene: Single and Double Kinetic Resolution Procedures

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A non-photochemical route to synthesize simple benzo[1,2-b:4,3-b′]dithiophenes: FeCl₃-mediated cyclization of dithienyl ethenes