22245-47-2Relevant academic research and scientific papers
Superacid-catalyzed dimerization/cyclization of isopropenyl-PAHs - Novel pathways to PAH dimers, phenalenes and their stable carbocations
Brule, Cedric,Sultana, Fatima,Hollenstein, Sandro,Okazaki, Takao,Laali, Kenneth K.
, p. 3700 - 3708 (2008)
The isopropenyl derivatives of representative classes of polycyclic aromatic hydrocarbons (PAHs) having four and five fused-ring systems, namely pyrene, chrysene, benzo[c]phenanthrene (BcPh), dibenzo[a,c]anthracene (benzo[f]tetraphene) and perylene, were synthesized by Wittig olefination from the corresponding acetyl-PAHs. Under the influence of triflic acid (TfOH), the isopropenyl derivatives were converted to novel PAH dimers and/or phenalenes in a simple one-pot procedure. A plausible mechanism for this process has been outlined, and the synthetic scope of this chemistry has been explored. Structural features in the PAH dimers were examined by DFT. As representative initial and final carbocation intermediates in the reaction sequence, stable carbocations derived from 3-isopropenylperylene and from 4,6,6-trimethyl-6H- dibenzo[a,kl]anthracene were generated and studied directly by NMR spectroscopy. The NMR characteristics and charge delocalization modes in the resulting benzylic carbocations are discussed. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
Synthesis and stable-ion studies of regioisomeric acetylnitropyrenes and nitropyrenyl carbinols and GIAO-DFT study of nitro substituent effects on α-pyrenyl carbocations
Laali, Kenneth K.,Arrica, Maria A.,Okazaki, Takao,Bunge, Scott D.
, p. 6093 - 6105 (2008)
Several regioisomeric acetylnitropyrenes were synthesized from isomeric acetylpyrenes by mild protic nitration. Nitration of 1-acetylpyrene gave the 3-, 6-, and 8-nitro derivatives (with 8-nitro as the major isomer), from which the corresponding carbinols [NO2-Py-CH(OH)CH3; Py = pyrene] were synthesized. Isomeric 4-acetylnitropyrenes and their corresponding carbinols were synthesized by starting from hexahydropyrene through nitration/aromatization/reduction or aromatization/nitration/reduction sequences. The molecular structures of 4-acetyl-3-nitropyrene and 1-(6-nitropyren-1-yl) ethanol were established by X-ray analysis. Tetrahydropyrene was the starting point for the synthesis of isomeric nitro-2-acetylpyrenes. Low-temperature protonation of 1-acetyl-8-nitropyrene, 4-acetyl-3-nitropyrene, and 2-acetyl-6-nitropyrene in FSO3H/SO 2ClF or in FSO3H/SbF5 (1:1)/SO2ClF resulted in the formation of onium dications (by C=O and NO2 protonation). Charge delocalization (pyrenium ion character) in the carboxonium ions is strongly influenced by the position of the carboxonium group, with the 4-acetyl-3-nitropyrene dication being the most delocalized. Superacid protonation of 1-(3-nitropyren-4-yl)ethanol gave a persistent onium dication rather than an α-pyrenyl carbocation. With all other isolated nitropyrenyl carbinol isomers, low-temperature protonation (with FSO3H/SO 2ClF) led to polymerization within 5 min standing at dry-ice-acetone temperature. For these cases, nitro substituent effects on the α-pyrenyl carbocations were gauged by DFT and GIAO-DFT studies. An interesting relationship between the computed nitro tilt angles and the GIAO-derived charge delocalization modes was observed. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
1-, 2-, and 4-ethynylpyrenes in the structure of twisted intercalating nucleic acids: Structure, thermal stability, and fluorescence relationship
Filichev, Vyacheslav V.,Astakhova, Irina V.,Malakhov, Andrei D.,Korshun, Vladimir A.,Pedersen, Erik B.
experimental part, p. 9968 - 9980 (2009/10/14)
A postsynthetic, on-column Sonogashira reaction was applied on DNA molecules modified by 2- or 4-io-dophenylmethylglycerol in the middle of the sequence, to give the corresponding ortho- and para-twisted intercalating nucleic acids (TINA) with 1-, 2-, and 4-ethynylpyrene residues. The convenient synthesis of 2- and 4-ethynylpyrenes started from the hydrogenolysis of pyrene that has had the sulfur removed and separation of 4,5,9,10-tetrahydropyrene and 1,2,3,6,7,8-hexahydropyrene, which were later converted to the final compounds by successive Friedel-Crafts acetylation, aromatization by 2,3-dichloro-5,6- dicyano-1,4-benzoquinone, and a Vilsmeier-Haack-Arnold transformation followed by a Bodendorf fragmentation. Significant alterations in thermal stability of parallel triplexes and antiparallel duplexes were observed upon changing the attachment of ethynylpyrenes from para to ortho in homopyrimidine TINAs. Thus, for para-TINAs the bulge insertion of an intercalator led to high thermal stability of Hoogsteen-type parallel triplexes and duplexes, whereas Watson-Crick-type duplexes were destabilized. In the case of ortho-TINA, both Hoogsteen and Watson-Crick-type complexeswere stabilized. Alterations in the thermal stability were highly influenced by the ethynylpyrene isomers used. This also led to TINAs with different changes in fluorescence spectra depending on the secondary structures formed. Stokes shift of approximately 100nm was detected for pyren-2-ylethynylphenyl derivatives, whereas values for 1- and 4-ethynylpyrenylphenyl conjugates were 10 and 40 nm, respectively. In contrast with paraTINAs, insertion of two ortho-TINAs opposite each other in the duplex as a pseudo-pair resulted in formation of an excimer band at 505 nm for both 1- and 4-ethynylpyrene analogues, which was also accompanied with higher thermal stability.
New fluorescent nucleoside derivatives - 5-alkynylated 2'-deoxyuridines
Korshun,Manasova,Balakin,Malakhov,Perepelov,Sokolova,Berlin
, p. 1809 - 1812 (2007/10/03)
Four fluorescent nucleosides, 5-(4-pyrenylethynyl)-, 5-(1- pyrenylbutadiynyl)-, 5-(3-perylenylethynyl)-, and 5-[4-(2- benzoxazolyl)phenylethynyl]-2'deoxyuridines, were synthesized.
Charge Delocalization Pathways in Persistent 1-Pyrenyl-, 4-Pyrenyl-, and 2-Pyrenylmethylcarbenium Ions as Models of PAH-Epoxide Ring Opening: NMR Studies in Superacids and AMI Calculations
Laali, Kenneth K.,Hansen, Poul Erik
, p. 5804 - 5810 (2007/10/03)
The relative stability, magnitude, and mode of charge delocalization into the pyrene moiety (Py) were evaluated for a series of tertiary and secondary 1-pyrenylmethylcarbenium ions PyC+R1R2 and PyC+R3
Aryl acetylenes as mechanism-based inhibitors of cytochrome P450- dependent monooxygenase enzymes
Foroozesh, Maryam,Primrose, Ginny,Guo, Zuyu,Bell, L. Chastine,Alworth, William L.,Guengerich, F. Peter
, p. 91 - 102 (2007/10/03)
Aryl acetylenes have been investigated as inhibitors of cytochrome P450 (P450)-dependent alkoxyresorufin dealkylation activities in liver microsomes prepared from rats exposed to β-naphthoflavone, isosafrole, or phenobarbital. Many of the acetylenes investigated produce pseudo-first- order time-dependent and NADPH-dependent losses of the dealkylation activities characteristic of mechanism-based irreversible inactivation (suicide inhibition). Replacing the terminal hydrogen of aryl acetylenes with a methyl group to convert ethynes into propynes enhances the inhibition of P450 1A enzymes; in some instances, this modification converts a reversible inhibitor of P450s into a suicide inhibitor. In contrast, ethynes are more effective suicide inhibitors of P450 2B-dependent dealkylations than the corresponding propynes. Aryl acetylenes with an ethynyl group on the 2 position of naphthalene or on the 9 position of phenanthrene and arylalkyl acetylenes with alkyl chains containing 2, 3, or 4 methylene groups are selective inhibitors of P450 2B1/2B2 in liver microsomes from rats. Aryl acetylenes also act as suicide inhibitors of P450 1A2 in human liver microsomes, of purified P450 1A2 from rabbit or rat liver in reconstituted systems, and of purified recombinant human P450 1A2 and 1A1 in reconstituted systems. 4-(1-Propynyl)biphenyl (4PBi) inactivated P450 1A2-dependent ethoxyresourfin deethylation (EROD) activity in human liver microsomes in an NADPH-dependent process (k(inactivation), 0.23 min-1; K1, 2.3 μM). 4PBi also inactivated purified recombinant human P450 1A2 (k(inactivation), 0.24 min-1; K(I), 4.3 μM). In agreement with previous reports [Yun, C.-H., Hammons, G. J., Jones, G., Martin, M. V., Hopkins, N. E., Alworth, W. L., and Guengerich, F. P. (1992) Biochemistry 31, 10556-10563], 2-ethyny]naphthalene (2EN) was not a suicide inhibitor of the P450 1A2 activity in human liver microsomes but did inactivate purified human P450 1A2. Neither 4PBi nor 2EN affected diagnostic activities of human microsomal P450 2E1, 2C9/10, 3A4, or 2C19. In the systems examined, the losses of P450-dependent activity produced by these aryl acetylenes were not accompanied by corresponding decreases in the measured P450 absorption spectra. Thus P450 inactivation by these aryl acetylenes does not involve labeling and destruction of the heme. Incubation of 4PBi with microsomal P450 1A1 or 1A2 from rat liver under conditions that lead to P450-dependent enzyme inactivations generates a 2-biphenylylpropionic acid product. This suggests that the suicide inhibition of P450s by propynylaryl acetylenes proceeds via a methylaryl ketene formed by a 1,2- methyl rearrangement, analogous to the mechanism of suicide inhibition by ethynyl acetylenes that proceed via ketene intermediates formed by 1,2- hydrogen shifts [Ortiz de Montellano, P. R., and Kunze, K. L. (1981) Arch. Biochem. Biophys. 209, 710-712].
Formation of sec-Alkylpyrenes by Friedel-Crafts and Cathodic Alkylation Methods. Structure and Spectroscopic Properties of Products. Catalytic Hydrogenation of Pyrene and Some Alkylpyrenes
Berg, Arne,Lam, Joergen,Hansen, Poul Erik
, p. 665 - 677 (2007/10/02)
Friedel-Crafts isopropylation of pyrene in neat isopropyl chloride yielded a series of mono, di, tri, tetra, and pentaisopropylpyrenes.Tetra and pentacyclopentyl- and cyclohexylpyrenes were formed analogously.Cathodic isopropylation by controlled potential electrolysis yielded both fully aromatic and partly hydrogenated isopropylpyrenes.Structure of these compounds, spectroscopic properties and mechanistic aspects of their formation are discussed.The catalytic hydrogenation (Raney nickel) of pyrene and isopropylpyrenes under very mild conditions has also been studied.
