| 1. |
- Xiong, Ruisheng, et al.
(author)
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Furan- and Thiophene-Based Auxochromes Red-shift Chlorin Absorptions and Enable Oxidative Chlorin Polymerizations
- 2017
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In: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 23:17, s. 4089-4095
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Journal article (peer-reviewed)abstract
- The de novo syntheses of chemically stable chlorins with five-membered heterocyclic (furane, thiophene, formylfurane and formylthiophene) substituents in selected meso- and beta-positions are reported. Heterocycle incorporation in the 3- and 13-positions shifted the chlorin absorption and emission to the red (up to lambdaem =680 nm), thus these readily incorporated substituents function analogously to auxochromes present in chlorophylls, for example, formyl and vinyl groups. Photophysical, theoretical and X-ray crystallographic experiments revealed small but significant differences between the behavior of the furan- and the thiophene-based auxochromes. Four regioisomeric bis-thienylchlorins (3,10; 3,13, 3,15 and 10,15) were oxidatively electropolymerized; the chlorin monomer geometry had a profound impact on the polymerization efficiency and the electrochemical properties of the resulting material. Chemical co-polymerization of 3,13-bis-thienylchlorin with 3-hexylthiophene yielded an organic-soluble red-emitting polymer.
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| 2. |
- Arkhypchuk, Anna I., et al.
(author)
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[2+2] Cycloaddition of phosphaalkenes as a key step for the reductive coupling of diaryl ketones to tetraaryl olefins
- 2022
-
In: Chemical Science. - : Royal Society of Chemistry. - 2041-6520 .- 2041-6539. ; 13:41, s. 12239-12244
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Journal article (peer-reviewed)abstract
- Procedures for the reductive coupling of carbonyl compounds to alkenes in the literature rely either on a radical coupling strategy, as in the McMurry coupling, or ionic pathways, sometimes catalysed by transition metals, as in more contemporary contributions. Herein, we present the first example of a third strategy that is based on the [2 + 2] cycloaddition of ketone-derived phosphaalkenes. Removal of P-trimethylsilyl groups at the intermediary 1,2-diphosphetane dimer results in its collapse and concomitant release of the tetraaryl-substituted alkene. In fact, the presented strategy is the only alternative to the McMurry coupling in the literature that allows tetraaryl alkene formation from diaryl ketones, with yields as high as 85%. The power of the methodology is illustrated in the reaction of tethered bis-benzophenones which engage in intramolecular reductive carbonyl couplings to form unusual macrocycles without the need for high dilution conditions or templating.
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| 3. |
- Arkhypchuk, Anna I., et al.
(author)
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Cascade Reactions Forming Highly Substituted, Conjugated Phospholes and 1,2-Oxaphospholes
- 2012
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In: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 51:31, s. 7776-7780
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Journal article (peer-reviewed)abstract
- The reaction of a phospha-Wittig–Horner reagent with diacetylenic ketones (see scheme) results in a cascade of reactions that can lead to both an oxaphosphole-terminated cumulene system and an alkene-bridged bis-phosphole. The reaction outcome is determined by the nature of the acetylene termini, with phenyl groups stabilizing a carbene intermediate that dimerizes to give the bis-phosphole product.
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| 4. |
- Arkhypchuk, Anna I., et al.
(author)
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Investigation of the demetallation of 10-aryl substituted synthetic chlorins under acidic conditions
- 2020
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In: Journal of Inorganic Biochemistry. - : ELSEVIER SCIENCE INC. - 0162-0134 .- 1873-3344. ; 205
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Journal article (peer-reviewed)abstract
- The acidic demetallation of a series of sparsely substituted Zn(II) chlorins is reported. The chlorins were functionalized in the 10-position with substituents ranging from strongly electron donating mesityl and p-methoxyphenyl to electron-withdrawingp-nitrophenyl and pentafluorophenyl groups. The demetallation kinetics were investigated using UV-Visible absorption spectroscopy. Demetallation was carried out by exposing the metallochlorins dissolved in CH2Cl2 to an excess of trifiuoroacetic acid. Reasonable correlation was found between the Hammett constant of the 10-substituent and the rate constant of the loss of the metal ion. The largest differences were observed between the p-methoxyphenyl and p-nitrophenyl-substituted Zn(II) chlorins, undergoing loss of Zn(II) with pseudo first order rate constants of 0.0789 x 10(-3) and 3.70 x 10(-3) min(-1), respectively. Taken together, these data establish the dramatic influence even subtle changes can have in altering the electronic properties of chlorins, which in turn impacts metallochlorin function.
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| 5. |
- Arkhypchuk, Anna I., et al.
(author)
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Isolation and Characterization of a Monoprotonated Hydroporphyrin
- 2018
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In: European Journal of Organic Chemistry. - : Wiley. - 1434-193X .- 1099-0690. ; :48, s. 7051-7056
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Journal article (peer-reviewed)abstract
- A simple protocol for the controlled preparation of mono- and diprotonated hydroporphyrins (chlorins) is presented. The chlorins carried 10-aryl groups with electron-neutral (phenyl), electron-donating (p-OMe-C6H4) or electron-withdrawing (pentafluorophenyl) substituents. The protonation reactions were readily followed by UV/Vis absorption spectroscopy, enabling the determination of the first (4.8-5.3) and second pK(a)'s (1.7-0.5). Both mono- and diprotonated species were fully characterized by H-1 NMR spectroscopy, which, in combination with theoretical studies, showed that these macrocycles were significantly distorted in solution. A 10-phenyl-substituted monoprotonated chlorin was characterized by X-ray crystallography. This is the first structurally characterized hydroporphyrin monocation, and the first crystal structure of a sterically unencumbered singly protonated tetrapyrrole. The photostabilities of the mono- and diprotonated 10-phenylchlorins were measured upon irradiation into their Soret bands; protonation yielded increased photostabilities.
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| 6. |
- Arkhypchuk, Anna I., et al.
(author)
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Mechanistic Insights and Synthetic Explorations of the Photoredox-Catalyzed Activation of Halophosphines
- 2023
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In: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 62:45, s. 18391-18398
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Journal article (peer-reviewed)abstract
- The light-driven activation of halophosphines R2PX (R = alkyl- or aryl, X = Cl, Br) by an IrIII-based photocatalyst is described. It is shown that initially formed secondary phosphines R2PH react readily with the remaining R2PX in a parent–child reaction to form diphosphines R2P–PR2. Aryl-containing diphosphines can be further reduced to secondary phosphines RAr2PH under identical photoredox conditions. Dihalophosphines RPX2 are also activated by the photoredox protocol, giving rise to unusual 3-, 4-, and 5-membered cyclophosphines. Transient absorption studies show that the excited state of the Ir photocatalyst is reductively quenched by the DIPEA (N,N-di-iso-propylethylamine) electron donor. Electron transfer to R2PX is however unexpectedly slow and cannot compete with recombination with the oxidized donor DIPEA•+. As DIPEA is not a perfectly reversible donor, a small proportion of the total IrII population escapes recombination, providing the reductant for the observed transformations.
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| 7. |
- Arkhypchuk, Anna I., et al.
(author)
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One-Pot Intermolecular Reductive Cross-Coupling of Deactivated Aldehydes to Unsymmetrically 1,2-Disubstituted Alkenes
- 2018
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In: Organic Letters. - : American Chemical Society (ACS). - 1523-7060 .- 1523-7052. ; 20:17, s. 5086-5089
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Journal article (peer-reviewed)abstract
- The phospha-Peterson reaction between a lithiated secondary phosphane, MesP(Li)TMS, and an aldehyde affords Mes-phosphaalkenes which, upon methanol addition and P-oxidation, react with a second carbonyl compound site specifically to produce unsymmetric alkenes. The E/Z selectivity of the one-pot cross coupling is largely determined by the electronic nature of the aryl substituent of the first aldehyde, with electron-donating groups giving rise to increased amounts of Z-alkenes.
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| 8. |
- Arkhypchuk, Anna I., et al.
(author)
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Oxaphospholes and Bisphospholes from Phosphinophosphonates and alpha,beta-Unsaturated Ketones
- 2013
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In: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 19:41, s. 13692-13704
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Journal article (peer-reviewed)abstract
- The reaction of a {W(CO)(5)}-stabilized phosphinophosphonate 1, (CO)(5)WPH(Ph)P(O)(OEt)(2), with ethynyl- (2a-f) and diethynylketones (7-11, 18, and 19) in the presence of lithium diisopropylamide (LDA) is examined. Lithiated 1 undergoes nucleophilic attack in the Michael position of the acetylenic ketones, as long as this position is not sterically encumbered by bulky (iPr)(3)Si substituents. Reaction of all other monoacetylenic ketones with lithiated 1 results in the formation of 2,5-dihydro-1,2-oxaphospholes 3 and 4. When diacetylenic ketones are employed in the reaction, two very different product types can be isolated. If at least one (Me)(3)Si or (Et)(3)Si acetylene terminus is present, as in 7, 8, and 19, an anionic oxaphosphole intermediate can react further with a second equivalent of ketone to give cumulene-decorated oxaphospholes 14, 15, 24, and 25. Diacetylenic ketones 10 and 11, with two aromatic acetylene substituents, react with lithitated 1 to form exclusively ethenyl-bridged bisphospholes 16 and 17. Mechanisms that rationalize the formation of all heterocycles are presented and are supported by DFT calculations. Computational studies suggest that thermodynamic, as well as kinetic, considerations dictate the observed reactivity. The calculated reaction pathways reveal a number of almost isoenergetic intermediates that follow after ring opening of the initially formed oxadiphosphetane. Bisphosphole formation through a carbene intermediate G is greatly favored in the presence of phenyl substituents, whereas the formation of cumulene-decorated oxaphospholes is more exothermic for the trimethylsilyl-containing substrates. The pathway to the latter compounds contains a 1,3-shift of the group that stems from the acetylene terminus of the ketone substrates. For silyl substituents, the 1,3-shift proceeds along a smooth potential energy surface through a transition state that is characterized by a pentacoordinated silicon center. In contrast, a high-lying transition state TS(E-F)(R=Ph) of 37kcalmol(-1) is found when the substituent is a phenyl group, thus explaining the experimental observation that aryl-terminated diethynylketones 10 and 11 exclusively form bisphospholes 16 and 17.
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| 9. |
- Arkhypchuk, Anna I., et al.
(author)
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Redox Switching in Ethenyl- Bridged Bisphospholes
- 2014
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In: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 20:49, s. 16083-16087
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Journal article (peer-reviewed)abstract
- A 2e(-)/2H(+) redox platform has been implemented in the ethenyl-bridged bisphosphol-3-ol 1 to afford the first phospholes that feature chemically reversible oxidations. Oxidation of the title compounds to the corresponding bisphosphol-3-one 2 leads to a change in conjugation topology and a concomitant hypsochromic shift of the lowest-energy absorption maximum by 100nm. Electrochemical oxidation proceeds without any detectable intermediates, whereas the deprotonated form of 1 can be observed in an aprotic medium during the reduction of 2. This dianionic intermediate 3 is characterized by end absorptions that are bathochromically shifted by circa 200nm compared to those of 2.
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| 10. |
- Arkhypchuk, Anna I., et al.
(author)
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Reductive Diphosphene Formation From W(CO)5-Coordinated Dichlorophosphanes
- 2011
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In: Phosphorus Sulfur and Silicon and the Related Elements. - : Informa UK Limited. - 1042-6507 .- 1563-5325. ; 186:4, s. 664-665
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Journal article (peer-reviewed)abstract
- A bis-[W(CO)(5)]-coordinated (Bu-t)(2)diphosphene was prepared from the corresponding [W(CO)(5)]-(BuPCl2)-Bu-t by treatment with LiAlH4.
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