Photocyclization Reaction Research Articles

Photocyclization Reactions of N-Substituted 3-(2-Hydroxynaphthalen-1-yl)propenamide Derivatives Accompanied by Liberation of Aliphatic and Aromatic Primary Amines

Photocyclization Reactions of N-Substituted 3-(2-Hydroxynaphthalen-1-yl)propenamide Derivatives Accompanied by Liberation of Aliphatic and Aromatic Primary Amines

Selective Photocyclization Reactions of (Z)-N-Acetyl-α-dehydro(9-phenanthryl)alanine Alkyl Esters and N′,N′-Dialkylamides to Dibenzo[f,h]isoquinoline Derivatives

Selective Photocyclization Reactions of (Z)-N-Acetyl-α-dehydro(9-phenanthryl)alanine Alkyl Esters and N′,N′-Dialkylamides to Dibenzo[f,h]isoquinoline Derivatives

Photocyclic Initiating System for Free Radical Photopolymerization Studied Through Holographic Recording

This paper discusses the efficiency of photocyclic initiating system (PCIS) based on a pyrromethene dye (EMP), an amine as electron donor (NPG) and an iodonium salt as electron acceptor (I250) under homogenous irradiation and holographic recording. It is shown that the PCIS is more efficient than the corresponding two component systems. This high efficiency is due to a photocyclic reaction that takes places during the irradiation, inducing the recovery of the dye in the ground state and the formation of two initiating radicals. The beneficial effect on the rate of grating formation and on the diffraction efficiency is clearly noticed. At high irradiation time, the fast polymerization observed with EMP-NPG-I250 even induces the polymerization in the dark fringes leading to a decrease of the holographic diffraction efficiency. This confirms the high performance of the photoinitiating system which can be used in holographic recording provided that the irradiation dose could be controlled.

Novel Naphthalene Based Lariat-Type Crown Ethers Using Direct Single Electron Transfer Photochemical Strategy

This study explored a direct SET-photochemical strategy to construct a new family of thioene conjugatednaphthalamide fluorophore based lariat-crown ethers which show strong binding properties towards heavy metal ions. Irradiations of designed nitrogen branched (trimethylsilyl)methylthio-terminated polyethylenoxytethered naphthalimides in acidic methanol solutions have led to highly efficient photocyclization reactions to generate naphthalamide based lariat type thiadiazacrown ethers directly in chemo- and regio-selective manners which undergo very facile secondary dehydration reactions during separation processes to produce their corresponding amidoenethio ether cyclic products tethered with electron donating diethyleneoxy- and diethyenethio-side arm chains. Fluorescence and metal cation binding properties of the lariat type enamidothio products were examined. The photocyclized amidoenethio products, thioene conjugated naphthalamide fluorophore containing lariat-thiadiazacrowns exhibited strong fluorescence emissions in region of 330-450 nm along with intramolecular exciplex emissions in region of 450-560 nm with their maxima at 508 nm. Divalent cation Hg 2+ and Pb 2+ showed strong binding to sulfur atom(s) in side arm chain and atoms in enethiadiazacrown ether rings which led to significant enhancement of fluorescence from its chromophore singlet excited state and concomitant quenching of exciplex emission. The dual fluorescence emission responses towards divalent cations might provide a new guide for design and development of fluorescence sensors for detecting those metals.

Facile synthesis of five 2D surface modifiers by highly selective photocyclic aromatization and efficient enhancement of oxygen permselectivities of three polymer membranes by surface modification using a small amount of the 2D surface modifiers

A facile synthesis of novel five 2D (planar) surface modifiers having a triphenylbenzene derivatives as a 2D structure has been achieved by the highly selective photocyclic aromatization reaction. Efficient enhancement of oxygen permselectivities through the three polymer membranes has been achieved by adding a small amount (<5.0 wt%) of the 2D surface modifiers. Among the five 2D surface modifiers, a modifier compound having oligoethylene oxide groups showed the best performance for the enhancement. These improvements were thought to be caused mainly by improvement of the solution selectivity on the membrane surface where the 2D surface modifiers were accumulated. In some of the surface-modified blend membranes, their plots in the PO2-α graph were over or close to the upper boundary line by Robeson in 1991. Since all the membranes containing the 2D surface modifiers showed better permselectivities than the corresponding substrate membranes, it is very promising for the future.

An Approach to the Carbon Backbone of Bielschowskysin, Part 1: Photocyclization Strategy

AbstractSeveral macrocyclization reaction attempts of highly advanced precursors toward a total synthesis of marine diterpene bielschowskysin are disclosed. Biomimetic [2+2]‐photocyclization reactions were applied to construct the cyclobutane core in these intermediates, which could be accessed along scalable high‐yielding reaction sequences from cheap enantiopure starting‐materials.

Chiral Photoresponsive Tetrathiazoles That Provide Snapshots of Folding States

Herein, we designed chiral photoresponsive tetra(2-phenylthiazole)s, which induce a diastereoselective 6π-electrocyclization reaction in a helically folded structure to freeze the conformational interconversions. The folding conformation with one helical turn of tetra(2-phenylthiazole)s was supported by multiple intramolecular noncovalent interactions including vicinal S···N interheteroatom interactions and CH-π and π-π stacking interactions between nonadjacent units, as found in X-ray crystal structures as well as quantum chemical calculations. The introduction of a chiral group at both ends of tetra(2-phenylthiazole) dictates the preferential folding into a one-handed helix conformation by the simultaneous operation of S···O and multiple CH-π interactions that involve the chiral end groups. Since the tetra(2-phenylthiazole)s possess two equivalent photoreactive 6π-electron systems and the folded conformation is suitable for photoinduced electrocyclization reaction, they undergo a photocyclization reaction in a stereoselective manner to memorize the chirality of the helix in a resulting diastereomeric closed form.

Synthesis New Photochromic Diarylethenes 1-(2,5-dimethyl thiazole)-2-[4-(2-cyanophenyl)-3-thienyl]} Perfluorocyclopentene

A unsymmetrical photochromic diarylethene, 1-(2,5-dimethyl thiazole)-2-[4-(2-cyanophenyl)-3-thieny} perfluorocyclopentene (1a),was synthesized, and its optoelectronic properties were also investigated in detail. The results showed that this compound exhibited reversible photochromism, changing from colorless to orange red after irradiation with UV light both in solution and in PMMA amorphous film.The open-ring isomer of the diarylethene 1 exhibited relatively strong fluorescence at 432 nm when excited at 384 nm. The fluorescence intensity declined along with the photochromism upon irradiation with 297 nm light.The diarylethene exhibited a fluorescence switches along with the photochromism from open-ring isomers to closed-ring isomers. When irradiated by UV light, the photocyclization reaction was occurred and the emission intensity of the diarylethene decreased significantly, due to producing the non-fluorescence closed-ring isomers. The back irradiation by appropriate wavelength visible light regenerated its open-ring isomers and recovered the original emission intensity.

Syntheses and Photochromic Properties of Thiophenophan-1-ene-S,S,S′,S′-tetraoxides

Abstract Photochromic thiophenophan-1-ene-S,S,S′,S′-tetraoxides have been synthesized by oxidation of sulfur atoms of thiophenophan-1-enes, and their photochromic properties were studied. The tetraoxides indicated photochromism and the quantum yields for photocyclization reactions became higher than that of nonbridged dithienylethene-S,S,S′,S′-tetraoxide due to fixation of conformations.

Photochemistry of Arabidopsis phototropin 1 LOV1: transient tetramerization

The photochemical reaction of the LOV1 (light-oxygen-voltage 1) domain of phototropin 1 from Arabidopsis thaliana was investigated by the time-resolved transient grating method. As with other LOV domains, an absorption spectral change associated with an adduct formation between its chromophore (flavin mononucleotide) and a cysteine residue was observed with a time constant of 1.1 μs. After this reaction, a significant diffusion coefficient (D) change (D of the reactant = 8.2 × 10(-11) m(2) s(-1), and D of the photoproduct = 6.4 × 10(-11) m(2) s(-1)) was observed with a time constant of 14 ms at a protein concentration of 270 μM. From the D value of the ground state and the peak position in size exclusion chromatography, we have confirmed that the phot1LOV1 domain exists as a dimer in the dark. The D-value and the concentration dependence of the rate indicated that the phot1LOV1 domain associates to form a tetramer (dimerization of the dimer) upon photoexcitation. We also found that the chromophore is released from the binding pocket of the LOV domain when it absorbs two photons within a pulse duration, which occurs in addition to the normal photocycle reaction. On the basis of these results, we discuss the molecular mechanism of the light dependent role of the phot1LOV1 domain.

Heterohelicenes with Embedded P‐Chiral 1H‐Phosphindole or Dibenzophosphole Units: Diastereoselective Photochemical Synthesis and Structural Characterization

The oxidative photocyclization reactions of olefins that contain 1H-phosphindole or dibenzophosphole substituents have been applied to the synthesis of P/N-bi-heterosubstituted dimeric helicenes, as well as of new [6]- and [8]phosphahelicenes. In these photocyclization processes, the configuration of the stereogenic phosphorus center dictates the sense of helical chirality. Thus, by starting from enantiomerically pure P-menthylphosphole-oxide units, this method affords enantiopure helical compounds. The helical phosphine oxides were characterized by X-ray diffraction. After reduction of the phosphine-oxides, the corresponding helical phosphines have been used as ligands in transition-metal complexes. The X-ray crystal structure of a gold chloride complex of a [6]helicene is reported.

ChemInform Abstract: Synthesis and Characterization of a New Chiral Pentacyclic Phosphine.

AbstractThe helically chiral pentacyclic phosphine (IX) containing a thiophene ring is obtained in a five‐step sequence via a Wittig reaction, a palladium‐catalyzed Mizoroki—Heck coupling, and classical oxidative photocyclization reactions.

Comparison of Photocyclization Reactions of Fluoro- vs Nonfluoro-Substituted Polymethyleneoxy Donor Linked Phthalimides

Photochemical reactions of fluoro- vs. nonfluoro-substituted polymethylenoxy chain linked phthalimide were carried out to explore how electronegative fluorine atoms inside the donor chain influence photocyclization reaction efficiencies and to briefly determine the alkali metal binding properties of the photoproducts. The results of this study show that the fluorine-substituted donor chain linked phthalimide undergoes inefficient photocyclization via single electron transfer (SET)-induced excited state pathways to generate 14-membered cyclic amidol compared to nonfluoro-analog due to low electron donor ability of the terminal oxygen donor site. These results show that photoinduced intramolecular SET processes arising from <TEX>${\alpha}$</TEX>-silyl ether electron donors to phthalimides are largely dependent on the kinds of substituents inside donor chain. Finally, a preliminary study with the cyclic amidols generated in this effort showed that they have weak alkali metal cation binding properties regardless of absence/presence of fluoro-substituents.

Synthesis and Characterization of a New Chiral Pentacyclic Phosphine

A new helically chiral pentacyclic phosphine, containing one thiophene ring, was prepared in good yield and purity via a five-step sequence involving a Wittig reaction, a palladium-catalyzed Mizoroki–Heck coupling, and classical oxidative photocyclization reactions. The investigation using ultraviolet–visible spectroscopy shows that the helicene precursor of the target helical phosphine as well as its phosphine oxide have interesting behaviors.

Synthesis of homofascaplysin B, C and analogues by the photocyclization of 3-acyl-2-chloro-1-[2-(indol-3-yl)ethyl]indoles

Two routes for the synthesis of homofascaplysin B, C and analogues have been established using the photocyclization as the key step. The first route is based on sequential photocyclization and photochemical dehydrogenation reactions of 2-chloro-3-acyl-1-[2-(indol-3-yl)ethyl]indoles in Cu(OAc)2- and air-saturated acetone; and the second is based on the two-step reactions, namely, photocyclization of 2-chloro-3-acyl-1-[2-(indol-3-yl)ethyl]indoles in acetone and DDQ-mediated dehydrogenation of 13-acyl-6,7-dihydro-pyrido[1,2-a;3,4-b′]diindoles in benzene at room temperature. Comparatively, the two-step route for the synthesis of homofascaplysin B, C and analogues is more efficient than the one-pot route.

Intramolecular photo-cyclization and consecutive rearrangement reactions of diazo-functionalized olefin-esters

Abstract A study on intramolecular photo-cyclization reactions with diazo-functionalized olefin-esters is presented. On irradiation of diphenyl diazo methane esters of cinnamic acids, not only the expected addition to the C C double bond is observed, yielding cyclopropanes, but also the addition to the carboxylic C O double bond is postulated as an intermediate. These formed intermediates undergo a rearrangement to cyclobutanones which further rearrange photo-assisted to oxetanes. Both were isolated and characterized. The reaction progress, the impact of the irradiation wavelength and solvent as well as the influence of the electron density of the olefin on the product distribution is described. Also, the detailed reaction mechanism for the photo-reaction cascade is discussed.

Synthesis and resolution of 2-hydroxyhexahelicene

2-Hydroxyhexahelicene has been prepared in good yield and purity via a three-step sequence involving palladium-catalysed Heck coupling and classical oxidative photocyclisation reactions. The two enantiomers of this hexacyclic helicenol have been separated using (S)-(−)-camphanoyl chloride as the chiral resolving agent.

Dynamics of Dangling Bonds of Water Molecules in pharaonis Halorhodopsin during Chloride Ion Transportation.

Ion transportation via the chloride ion pump protein pharaonis halorhodopsin (pHR) occurs through the sequential formation of several intermediates during a photocyclic reaction. Although the structural details of each intermediate state have been studied, the role of water molecules in the translocation of chloride ions inside of the protein at physiological temperatures remains unclear. To analyze the structural dynamics of water inside of the protein, we performed time-resolved Fourier transform infrared (FTIR) spectroscopy under H2O or H2(18)O hydration and successfully assigned water O-H stretching bands. We found that a dangling water band at 3626 cm(-1) in pHR disappears in the L1 and L2 states. On the other hand, relatively intense positive bands at 3605 and 3608 cm(-1) emerged upon the formation of the X(N) and O states, respectively, suggesting that the chloride transportation is accompanied by dynamic rearrangement of the hydrogen-bonding network of the internal water molecules in pHR.

Co-Crystals and Salts Obtained from Dinitrogen Bases and 1,2,3,4-Cyclobutane Tetracarboxylic Acid and the Use of the Latter As a Template for Solid-State Photocyclization Reactions

The synthesis, isolation, and characterization of a series of co-crystals and adducts of 1,2,3,4-cyclobutane tetracarboxylic acid (H4CBTC) with the dinitrogen bases 1,2-bis(4-pyridyl)ethane (BPA) and 1,2-bis(4-pyridyl)ethylene (BPE), respectively, are reported. The thermal stability and interconversion process between the dihydrated salt [BPAH2][H2CBTC]·2H2O and its dehydration product and the use of this latter to obtain the neutral co-crystal [BPA]2·[H4CBTC] have been investigated. The products obtained with 1,2-bis(4-pyridyl)ethylene (BPE), namely, the salt [BPEH][H3CBTC] and the co-crystal [BPE]2·[H4CBTC] are prearranged in space so as to be able to react photochemically yielding rctt-tetrakis(4-pyridyl)cyclobutane (TPCB). Recrystallization from ethanol of the photocyclization products yields the channeled structure of the solvated co-crystal [TPCB]·[H4CBTC]·EtOH.

New thermally stable photochromic di(het)arylethenes of the cyclopentenone series

Oxidation of 2,3-diarylcyclopent-2-en-1-ones with m-chloroperoxybenzoic acid gave new thermally stable sulfone derivatives of photochromic diarylethenes. The spectral properties of the compounds obtained (the wavelengths of the maxima of the absorption bands of their initial and cyclic forms, the quantum yields of photocyclization and photobleaching reactions) as well as their thermal stability and fatigue resistance were examined. The relationship between the structures of the synthesized compounds and their photochromic properties was determined. The energy differences between the ground-state molecules of the starting and photoinduced isomers of 2,3-diarylcyclopent-2-en-1-ones were calculated by the DFT/B3LYP1 method with the 6-31G(d) basis set. The calculated energy differences can be used to predict and explain such spectral characteristics of photochromic diarylethenes as the thermal stability of photoinduced isomers and the quantum yields of cycloreversion reactions.