16914-68-4Relevant articles and documents
Systematic investigations on fused π-system compounds of seven benzene rings prepared by photocyclization of diphenanthrylethenes
Fujino, Shota,Yamaji, Minoru,Okamoto, Hideki,Mutai, Toshiki,Yoshikawa, Isao,Houjou, Hirohiko,Tani, Fumito
, p. 925 - 934 (2017)
We studied the photoproducts of 1-(n-phenanthryl)-2-(m-phenanthryl)ethenes (nEm; n, m = 1, 3 and 9) for understanding photocyclization patterns based on NMR spectroscopy. The crystal structures of the photoproducts were analyzed by X-ray crystallography, and the photophysical features of the photocyclized molecules were investigated based on emission and transient absorption measurements. Phenanthrene derivatives substituted at the 1- and 3-positions were prepared for synthesizing nEm by photocyclization of stilbene derivatives. We obtained four types of primary photoproducts (n@m) from the corresponding nEm. Two of them were found to have racemic molecular structures in the single crystal determined by X-ray crystallography. Besides the primary photoproducts, two types of secondary photoproducts (n@mPP) were isolated. Fluorescence quantum yields and lifetimes of the obtained photoproducts were determined in solution whereas the definite fluorescence quantum yields were obtained in the powder. Observation of the triplet-triplet absorption spectra in solution by laser photolysis techniques showed that intersystem crossing to the triplet state competes with the fluorescence process.
Origin of the Preferential Formation of Helicenes in Mallory Photocyclizations. Temperature as a Tool to Influence Reaction Regiochemistry
Weber,Clennan
, p. 817 - 830 (2019)
The regiochemistry of four bis-Mallory photocyclization substrates has been examined from experimental and computational perspectives. Formation of all three possible regioisomers was only observed in the reaction of one of the substrates. In the other three substrates, only the two C2-symmetric products, but not the C1 product, were formed. In the three reactions that only formed two products, the photocyclization temperature could be used to select for exclusive formation of one or the other regioisomer. The use of temperature to select between two regioisomers also worked in the photocyclization of the substrate that formed three products. However, no temperature was located for exclusive formation of the third component, one of the C2-symmetric products, which always formed alongside either one or both of its regioisomers. B3LYP/6-311+G(2d,p) calculations were used to determine the energies of all of the dihydrophenanthrene (DHP), tetrahydrophenanthrene (THP), and mono-Mallory photocyclization intermediates. The oscillator strengths of the DHP precursors to the helicene products were a factor of 4.8-9.2 smaller than those of competitively formed DHPs. This observation suggests that establishment of a photostationary state is responsible for the preferential formation of helicenes that has been observed as a unique and useful feature of many Mallory photocyclizations.
Synthesis of carbohelicenes and derivatives by 'carbenoid couplings'
Gingras, Marc,Dubois, Fabien
, p. 1309 - 1312 (1999)
Short synthetic sequences to carbohelicenes have been achieved under thermal conditions, without using photochemistry and high dilution. Couplings of aromatic bis(bromomethyl) moieties, in the presence of an excess of LiHMDS, are key reactions in the final ring closures to carbohelicenes. These optimized, quick and efficient reactions occur at 0°C within 10 min. and often provide [5]-helicene, [5]-helicene derivatives and [7]-helicene in ~ 75% yield. Preliminary data questioned the formation of carbenoid anions and carbenes in the so called 'carbenoid couplings'.
Modified synthesis of heftahelicene and its resolution into single enantiomers
Alexandrova, Zuzana,Sehnal, Petr,Stara, Irena G.,Stary, Ivo,Saman, David,Urquhart, Stephen G.,Otero, Edwige
, p. 1256 - 1264 (2006)
A practical synthesis of racemic heptahelicene has been develeped being based on key [2+2+2] cycloisomerization of bis[2-(but-3-yn-1-yl)-1-naphthyl] acetylene under CpCo(CO)2/PPh3 or CpCo(C2H 4)2 catalysis. The application of the Ni(COd)2 catalyst with (-)-(Sa)-(2′-methoxy-1,1′-binaphthalen-2- yl)diphenylphosphane resulted in enantioselective triyne cyclization to provide (+)-7,8,11,12-tetrahydroheptahelicene in 40% ee. Optically pure (-)-(M)- and optically highly enriched (+)-(P)-heptahelicene were obtained on a milligram scale by resolution of racemate by chiral HPLC on a semipreparative Whelk-O1 column.
Expeditious synthesis of helicenes using an improved protocol of photocyclodehydrogenation of stilbenes
Talele, Harish R.,Chaudhary, Anju R.,Patel, Parthiv R.,Bedekar, Ashutosh V.
experimental part, p. 15 - 37 (2011/06/19)
An improved procedure has been developed for photodehydrocyclization of stilbenes for the synthesis of phenanthrenes and helicenes. This procedure involves the use of THF as a scavenger of hydriodic acid produced during iodine mediated photodehydrocyclization. The use of THF is advantageous due to its higher boiling point, lower cost and easy availability as compared to propylene oxide. The method is applied to synthesize a number of phenanthrenes and helicenes. ARKAT-USA, Inc.
Preparation of helicenes through olefin metathesis
Collins, Shawn K.,Grandbois, Alain,Vachon, Martin P.,Cote, Julie
, p. 2923 - 2926 (2007/10/03)
(Chemical Equation Presented) Metathesis with a twist! A ring-closing-metathesis strategy has been developed for the preparation of various substituted [5]helicene motifs and [6]- and [7]helicenes. The two optimized protocols include one method that utilizes the Grubbs second-generation catalyst under microwave-irradiation conditions and another that employs a modified Grubbs-Hoveyda catalyst at 40°C in a sealed reaction vessel. (Mes = mesityl).
An alternative procedure for the synthesis of [5]- and [7]carbohelicenes
El Abed, Riadh,Hassine, Bechir Ben,Genet, Jean-Pierre,Gorsane, Mohamed,Marinetti, Angela
, p. 1517 - 1522 (2007/10/03)
2-Bromo[5]helicene derivatives and substituted [7]helicenes have been prepared through a synthetic sequence relying on Heck-type and photocyclodehydrogenation reactions. This procedure provides a new, versatile and efficient approach to helicene derivativ
Synthesis of [5]-, [6]-, and [7]helicene via Ni(0)- or Co(I)-catalyzed isomerization of aromatic cis,cis-dienetriynes
Teply, Filip,Stara, Irena G.,Stary, Ivo,Kollarovic, Adrian,Saman, David,Rulisek, Lubomir,Fiedler, Pavel
, p. 9175 - 9180 (2007/10/03)
An original approach to helicene frameworks exploiting atom economic isomerization of appropriate energy-rich aromatic cis,cis-dienetriynes has been developed. The new paradigm provides nonphotochemical syntheses of helicenes based on the easy, convergent, and modular assembly of key cis,cis-dienetriynes and their nickel(0)-catalyzed [2+2+2] cycloisomerization. The potential of the methodology is underlined by the syntheses of the parent [5]helicene (2), 7,8-dibutyl[5]helicene (23), [6]helicene (24), and [7]helicene (25). The approach can be adapted to prepare functionalized helicenes as exemplified by the eight-step synthesis of 7,8-dibutyl-2,3-dimethoxy[6]helicene (34). Density functional theory (DFT) calculations showed that bis[2-((1Z)-1-buten-3- ynyl)phenyl]acetylene (1) and isomeric [5]helicene (2) differ enormously in the Gibbs energy content (ΔG= -136.6 kcal.mol-1) to favor highly the devised intramolecular simultaneous construction of three aromatic rings.
DIRECTIVE EFFECT OF BROMINE ON STILBENE PHOTOCYCLIZATIONS. AN IMPROVED SYNTHESIS OF HELICENE
Sudhakar, Anantha,Katz, Thomas J.
, p. 2231 - 2234 (2007/10/02)
Bromine atoms direct photocyclizations away both from positions they occupy and from those adjacent, providing previously unavailable selectivities in syntheses of helicenes.
HELICENES : SYNTHESE PHOTOCHIMIQUE ET ETUDE RMN 19F, 13 C ET 1H DE FLUORO-1-HEXAHELICENES ET FLUORO-1-HEPTAHELICENES.
Corsane, M.,Defay, N.,Martin, R. H.
, p. 215 - 232 (2007/10/02)
1-Fluorohexahelicene, 1-fluoroheptahelicene and 12 substituted derivatives of these fluorohelicenes have been synthesized by the photocyclodehydrogenation of 1-fluro-11-styrylbenzophenanthrenes (Table 2) and 1-fluoro-13-styrylpentahelicenes (Table 4) respectively.The photocyclisations to heptahelicenes were accompanied in five cases, by a side reaction, namely a photodefluoration.A new synthesis of heptahelicenes is described (25-->18 : 40 percent). 1H, 19F and 13C-NMR spectra are discussed. 19F and 13C-NMR spectra of 1-fluoro-, 1-fluoro-13-methyl- and 1-fluoro-13-methoxycarbonylpentahelicene (8d, 8a and 8 R=-CO2CH3) are also included.
