[2+2+2] Cycloisomerisation of Aromatic Cyanodiynes in the Synthesis of Pyridohelicenes and Their Analogues

Klívar, Jiří; Jančařík, Andrej; Šaman, David; Pohl, Radek; Fiedler, Pavel; Bednářová, Lucie; Starý, Ivo; Stará̈, Irena G.

doi:10.1002/chem.201602747

Cited by 47 publications

(34 citation statements)

References 53 publications

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“…78a 1 and 78a 2 , respectively (Scheme 19). Furthermore, while these N-containing [6]helicenes were obtained as racemic mixtures only, 126 the enantioselective synthesis of dibenzo-carbo [6]helicene (P)-80 bearing two tolyl groups in positions 9 and 10 were reported when using Ni(COD) 2 /(R)-QUINAP as the catalytic system. 125 Scheme 19.…”

Section: [2+2+2] Alkyne Cyclotrimerizationmentioning

confidence: 99%

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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: [2+2+2] Alkyne Cyclotrimerizationmentioning

confidence: 99%

“…Stereoselective synthesis of tolyl-substituted azahelicenes. 126,128 Table 7. Specific rotation values of enantioenriched tolyl-substituted azahelicenes.…”

Section: Scheme 20mentioning

confidence: 99%

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

2019

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“…The [2+ +2+ +2] cycloaddition reaction involving two alkynes and one nitrile is an excellent optionf or de novo construction of polysubstituted pyridines in as ingle reaction step [16] and may allow the preparation of pyridohelicene-like derivatives. In am ore recent study, [17] the same research group prepared two different chiral cyanodiynes with (R)c onfiguration, 68 and 69, and submitted them to ac ycloaddition process under cobalt catalysis (Scheme 13). The cycloaddition of enantiomerically pure 68 and 69 promoted by substoichiometric amounts of [CpCo(CO) 2 ]c omplex and PPh 3 as al igand under microwave irradiation afforded pyrido [5]helicene-liked erivative 70 and pyrido [6]helicene-like derivative 71,r espectively,i ng ood yields and in ac ompletely diastereoselective process.T he authors postulated that this efficient stereocontrol was due to the 1,3allylic-type strain [18] between the methyl group at the stereogenic center and the tolyl group.…”

Section: Central-to-helical Chiral Induction In [2+ +2+ +2] Cycloaddimentioning

confidence: 99%

Chiral Induction in [2+2+2] Cycloaddition Reactions

Pla‐Quintana

Roglans

2018

Asian J Org Chem

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Chiral compounds containing six-membered rings, whether aromatic or not, are of interesti nawide range of disciplines, including materials cience, medicinal chemistry, and agrochemistry.A st ransition-metal-catalyzed[ 2 + +2+ +2] cycloaddition reactions are one of the most elegant routes for the construction of six-memberedr ings, significant effort has been given to developing asymmetric variants.I nt his focus review, we bring together the work that has been done in optimizing diastereoselective [2+ +2+ +2] cycloaddition reactions of enantiomerically pure substrates. Twod ifferent approaches-chirality inductiona nd chirality transfer-are considered in ar eview organized by the typeo fc hiral element being constructed (central, axial, or helical). The general challenges that are involved are highlighted and possible future directions in the field are discussed.The ORCID identification number(s) for the author (s) of this articlecan be found under: https://doi.org/10.1002/ajoc.201800291. Scheme1.Transition-metal-catalyzed [2+ +2+ +2] cycloadditions of three alkynes. Scheme2.Postulated generalmechanism of [2+ +2+ +2] cycloaddition reaction of three alkynes,w here M = transition-metal catalyst. Scheme3.Co-mediated [2+ +2+ +2] cycloadditions of enediynes containing cyclic chiralp hosphine oxides. Scheme14. Co-mediated [2+ +2+ +2] cycloadditions of enantiopuretriynes 72-78 to afford non-racemic helicene-like derivatives 79-85. Scheme15. Co-mediated [2+ +2+ +2] cycloadditions of enantiopuretriynes 86-87 to afford non-racemic [6] and [7]helicene-like derivatives. Scheme16. Co-catalyzed [2+ +2+ +2] cycloadditions of enantiopure triynes 90-92 to affordnon-racemic [5] and [6]helicene-like derivatives.

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“…[1] For example, we reportedt he design and enantioselective synthesis of dibenzo-fused helicenes (1,1-bitriphenylenes)b yr hodium(I)-catalyzed enantioselective intermolecular[ 2 + +2+ +2] cycloaddition [2][3][4][5] of biaryl-linked tetraynes with carbonyl-linked diynes.T he thus-obtained [7]helicenes exhibited high anisotropies of circularly polarized luminescence (CPL [6] )w ithm oderate fluorescenceq uantum yields. [1] For example, we reportedt he design and enantioselective synthesis of dibenzo-fused helicenes (1,1-bitriphenylenes)b yr hodium(I)-catalyzed enantioselective intermolecular[ 2 + +2+ +2] cycloaddition [2][3][4][5] of biaryl-linked tetraynes with carbonyl-linked diynes.T he thus-obtained [7]helicenes exhibited high anisotropies of circularly polarized luminescence (CPL [6] )w ithm oderate fluorescenceq uantum yields.…”

Section: Introductionmentioning

confidence: 99%

“…Helicenes having uncommon extended p conjugation have attracted much attention as chiral luminescence materials. [1] For example, we reportedt he design and enantioselective synthesis of dibenzo-fused helicenes (1,1-bitriphenylenes)b yr hodium(I)-catalyzed enantioselective intermolecular[ 2 + +2+ +2] cycloaddition [2][3][4][5] of biaryl-linked tetraynes with carbonyl-linked diynes.T he thus-obtained [7]helicenes exhibited high anisotropies of circularly polarized luminescence (CPL [6] )w ithm oderate fluorescenceq uantum yields. [4i, 7] Starý,S tarµ,a nd co-workers recentlyr eported the enantioselective synthesis of dibenzo [7]helicenes with up to 86 % ee by nickel(0)-catalyzed intramolecular [2+ +2+ +2] cycloadditiono f2 -phenylnaphthalene-linked triynes,w hereast heir structures and photophysical/chiroptical properties were not examined, and highly enantioselective transformation was limited to the case of at erminal triyne for dibenzo [7]helicenes.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Single and Double Dibenzohelicenes by Rhodium‐Catalyzed Intramolecular [2+2+2] and [2+1+2+1] Cycloaddition

Yamano

Shibata

Tanaka

2018

Chemistry A European J

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Dibenzo[7]helicenes were synthesized with up to 99 % ee by rhodium(I)/binap-catalyzed enantioselective intramolecular [2+2+2] cycloaddition of 2-phenylnaphthalene-linked triynes. Additionally, [2+1+2+1] cycloaddition products, that is, twisted anthracenes, were also synthesized by using difluorphos as ligand. Although these compounds are not configurationally stable at elevated temperature, their Scholl reactions afforded configurationally stable double dibenzo[6]helicenes. The thus-obtained dibenzo[7]helicene exhibited good circularly polarized luminescence property and the double dibenzo[6]helicene showed high fluorescence quantum yield.

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[2+2+2] Cycloisomerisation of Aromatic Cyanodiynes in the Synthesis of Pyridohelicenes and Their Analogues

Cited by 47 publications

References 53 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)

Chiral Induction in [2+2+2] Cycloaddition Reactions

Synthesis of Single and Double Dibenzohelicenes by Rhodium‐Catalyzed Intramolecular [2+2+2] and [2+1+2+1] Cycloaddition

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