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Search for "photochemistry" in Full Text gives 160 result(s) in Beilstein Journal of Organic Chemistry.
New core-pyrene π structure organophotocatalysts usable as highly efficient photoinitiators
Beilstein J. Org. Chem. 2013, 9, 877–890, doi:10.3762/bjoc.9.101
- ; photocatalysts; photoinitiators; radical photopolymerization; Introduction Free radical sources are encountered in various areas such as organic chemistry, biochemistry and polymer chemistry. In the field of polymer photochemistry applied to photopolymerization reactions, they are referred to as photoinitiators
Spectroscopic characterization of photoaccumulated radical anions: a litmus test to evaluate the efficiency of photoinduced electron transfer (PET) processes
Beilstein J. Org. Chem. 2013, 9, 800–808, doi:10.3762/bjoc.9.91
- hand, the very structure of electronically excited states makes them both easily oxidized (by donating the electron promoted to an empty orbital) and reduced (an electron is transferred to the low-lying semi-occupied orbital). As a result, redox reactions are quite common in photochemistry and occur
- aromatic compounds known to participate in photosubstitution or photocatalytic alkylation reactions. It was proposed to ascertain whether these may accumulate, as often observed in electrochemistry [33][34] and by pulse radiolysis [35], but rarely in photochemistry. Results The acceptors chosen for this
4-Pyridylnitrene and 2-pyrazinylcarbene
Beilstein J. Org. Chem. 2013, 9, 754–760, doi:10.3762/bjoc.9.85
- -diazacyclohepta-1,2,4,6-tetraene (20). Further photolysis causes ring opening to the ketenimine 27. Keywords: carbene–nitrene interconversion; diazepines; flash vacuum thermolysis; matrix photochemistry; nitrile ylides; reactive intermediates; Introduction The carbene–nitrene interconversion exemplified with
3-Pyridylnitrene, 2- and 4-pyrimidinylcarbenes, 3-quinolylnitrenes, and 4-quinazolinylcarbenes. Interconversion, ring expansion to diazacycloheptatetraenes, ring opening to nitrile ylides, and ring contraction to cyanopyrroles and cyanoindoles
Beilstein J. Org. Chem. 2013, 9, 743–753, doi:10.3762/bjoc.9.84
- either the nitrenes or the diazacycloheptatetraenes to nitrile ylides. Keywords: carbene-nitrene interconversion; diazepines; flash vacuum thermolysis; matrix photochemistry; nitrile ylides; reactive intermediates; Introduction A multitude of rearrangements of heterocyclic nitrenes have been described
Electron and hydrogen self-exchange of free radicals of sterically hindered tertiary aliphatic amines investigated by photo-CIDNP
Beilstein J. Org. Chem. 2013, 9, 437–446, doi:10.3762/bjoc.9.46
- agreement between experimental and calculated values of ∆G‡298. Keywords: amines; CIDNP; electron transfer; free radicals; hydrogen transfer; ketones; kinetics; photochemistry; self-exchange; Introduction Sensitized hydrogen abstractions from tertiary aliphatic amines present a mechanistic spectrum with a
A chemist and biologist talk to each other about caged neurotransmitters
Beilstein J. Org. Chem. 2013, 9, 64–73, doi:10.3762/bjoc.9.8
- glutamate itself onto neurons [35]. Since these original reports, many other groups have reproduced these results, so they are probably reliable. A recently developed caged glutamate that uses different photochemistry ("RuBi-Glu") is also reported to be inert towards AMPA receptors [33]. This study also
Flow photochemistry: Old light through new windows
Beilstein J. Org. Chem. 2012, 8, 2025–2052, doi:10.3762/bjoc.8.229
- Jonathan P. Knowles Luke D. Elliott Kevin I. Booker-Milburn School of Chemistry, University of Bristol, Cantock’s Close, Bristol, BS8 1TS, UK. 10.3762/bjoc.8.229 Abstract Synthetic photochemistry carried out in classic batch reactors has, for over half a century, proved to be a powerful but under
- -utilised technique in general organic synthesis. Recent developments in flow photochemistry have the potential to allow this technique to be applied in a more mainstream setting. This review highlights the use of flow reactors in organic photochemistry, allowing a comparison of the various reactor types to
- be made. Keywords: cycloaddition; flow chemistry; photocatalysis; photochemistry; photooxygenation; Introduction The use of ultraviolet light to carry out bond-forming reactions in synthetic organic chemistry has a long history dating back to the mid-19th century. The observation by Trommsdorff [1
Cyclodextrin nanosponge-sensitized enantiodifferentiating photoisomerization of cyclooctene and 1,3-cyclooctadiene
Beilstein J. Org. Chem. 2012, 8, 1305–1311, doi:10.3762/bjoc.8.149
- the photochirogenic reaction. Keywords: cyclodextrins; 1,3-cyclooctadiene; cyclooctene; nanosponge; photochirogenesis; photoisomerization; Introduction The precise control of chiral photoreactions, or photochirogenesis, is one of the most challenging topics in current photochemistry [1][2][3]. Weak
- intermolecular interactions, short lifetime and high reactivity of the excited-state substrate are the major causes that prevent efficient asymmetric induction in chiral photochemistry. A supramolecular approach to photochirogenesis provides a convenient and also promising tool to facilitate the excited-state
- the product by adding alcohol. The latter result in particular revealed the active roles of chiral voids in CDNS as novel photochirogenic reaction media, encouraging the further application of CDNS to chiral photochemistry. (a) Circular dichroism spectra of 3 (67 μg/mL) (black), 4 (67 μg/mL) (red) and
Photochemistry with laser radiation in condensed phase using miniaturized photoreactors
Beilstein J. Org. Chem. 2012, 8, 1213–1218, doi:10.3762/bjoc.8.135
- Toxicology and Genetics, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen, Germany 10.3762/bjoc.8.135 Abstract Miniaturized microreactors enable photochemistry with laser irradiation in flow mode to convert azidobiphenyl into carbazole with high efficiency
- alternative method enabled by the maturing microreaction technology and the use of flow chemistry [4][5][6] is the integration of synthesis and screening in one integrated lab-on-a-chip approach [7]. Using this methodology we have integrated photochemistry in a miniaturized reaction setup to enable
- combinatorial flow chemistry in lab-on-a-chip applications. Photochemical processes are in this case particularly interesting because of their enhanced molecular activation [8]. Photochemistry in microreactors is an emerging research area [9], and especially photocatalytic reactions have been investigated in
Photoreactions of cyclic sulfite esters: Evidence for diradical intermediates
Beilstein J. Org. Chem. 2012, 8, 1208–1212, doi:10.3762/bjoc.8.134
- Rick C. White Benny E. Arney Jr. Heiko Ihmels Department of Chemistry, Sam Houston State University, Huntsville, TX 77341, USA Department of Chemistry, Universität Siegen, Adolf-Reichwein-Str. 2, 57068 Siegen, Germany 10.3762/bjoc.8.134 Abstract The photochemistry of a phenyl and 1,2-diphenyl
- considered. Keywords: diradicals; mechanisms; photochemistry; Introduction Photoinduced ring-opening or ring-fragmentation processes constitute an important type of reaction in organic photochemistry and have been examined both from a mechanistic and a synthetic point of view [1][2][3][4][5]. Mechanistic
- in the photochemistry of vicinal diaryloxiranes based on the photochemical formation of methyl ethers in methanol solution [8]. Mechanistically, stereoselective oxygen scrambling was found in the photoextrusion of carbon dioxide from benzyl benzoate esters [9]. Furthermore, photodecarboxylation
Control over molecular motion using the cis–trans photoisomerization of the azo group
Beilstein J. Org. Chem. 2012, 8, 1071–1090, doi:10.3762/bjoc.8.119
- fluorescent dye close to the photoswitch giving rise to a fluorescence change upon isomerization. The introduction of azobenzene-modified biomolecules in zebrafish proved that the photochemistry of azobenzenes was similar in vivo and in vitro, and that appropriate azobenzenes could be stable in vivo for days
Recent advances towards azobenzene-based light-driven real-time information-transmitting materials
Beilstein J. Org. Chem. 2012, 8, 1003–1017, doi:10.3762/bjoc.8.113
- devices. Many different organic photochromic molecules are known in photochemistry, such as azobenzenes, stilbenes, spiropyranes, fulgides, diarylethenes and chromenes among many others (Figure 1) [16]. The photochromic processes that take place when such compounds are illuminated can be divided in three
meta-Oligoazobiphenyls – synthesis via site-selective Mills reaction and photochemical properties
Beilstein J. Org. Chem. 2012, 8, 877–883, doi:10.3762/bjoc.8.99
- , however, only one azobenzene unit is incorporated. One of the reasons is the synthetic challenge associated with the preparation of such oligomers. Solubility and, especially, selectivity issues have to be addressed. Another reason is the higher complexity of the photochemistry of these multi-photochromic
Synthesis and photooxidation of styrene copolymer bearing camphorquinone pendant groups
Beilstein J. Org. Chem. 2012, 8, 337–343, doi:10.3762/bjoc.8.37
- (CQ) in the presence of H-atom donors such as ethers (H abstraction), or more efficiently tertiary amines (electron/proton transfer), is known to be an effective photoinitiator for curing methacrylate-based dental restorative resins [1][2][3][4][5][6][7][8][9]. CQ photochemistry in solution in the
- subsequent reactions leading to photoproducts [21]. The rate-determining step in photoinitiation by CQ/amine is hydrogen transfer by the excited n→π* triplet state of the carbonyl group of CQ from the alkylamino group [8][9]. The photochemistry of the low molecular CQ in the polystyrene (PS) film was the
- literature [31]. The goal of this work was to prepare a more easily accessible racemic MCQ and to compare the photochemistry of MCQ/S with that of low molecular CQ in PS films in the presence of oxygen. Results and Discussion Synthesis of MCQ Racemic MCQ was synthesized in seven steps from (±)-10
Continuous flow photolysis of aryl azides: Preparation of 3H-azepinones
Beilstein J. Org. Chem. 2011, 7, 1124–1129, doi:10.3762/bjoc.7.129
- reaction conditions using the flow reactor allowed minimization of secondary photochemical reactions. Keywords: azepinones; azides; continuous flow; nitrenes; photochemistry; Findings Although photochemical rearrangements are an important class of reactions for heterocycle synthesis [1][2], their use is
Microphotochemistry: 4,4'-Dimethoxybenzophenone mediated photodecarboxylation reactions involving phthalimides
Beilstein J. Org. Chem. 2011, 7, 1055–1063, doi:10.3762/bjoc.7.121
- superior results thus proving the superiority of microphotochemistry over conventional technologies. Keywords: microflow; microreactor; photochemistry; photodecarboxylation; phthalimide; Introduction Organic photochemistry is a highly successful synthesis method that allows the construction of complex
- molecules with a “flick of a switch” [1][2][3][4]. Light is furthermore considered a clean “reagent” and consequently, photochemistry has contributed extensively to the growing field of Green Chemistry [5][6][7]. It is therefore surprising that synthetic organic photochemistry has been widely neglected by
- the chemical industry. In fact, most photochemical production processes in industry were developed and realized decades ago [8][9][10][11]. A major drawback of photochemistry as a modern research and development (R&D) tool has been the usage of specialized reactors and lamps, which are often
Chemistry in flow systems II
Beilstein J. Org. Chem. 2011, 7, 1046–1047, doi:10.3762/bjoc.7.119
- highlight three areas. First of all, we have the application to photochemistry, which has the chance of experiencing a renaissance particularly in an industrial environment. Second, flow chemistry lends itself naturally to the synthesis and direct application of reactive intermediates or reactive reagents
Fine-tuning alkyne cycloadditions: Insights into photochemistry responsible for the double-strand DNA cleavage via structural perturbations in diaryl alkyne conjugates
Beilstein J. Org. Chem. 2011, 7, 813–823, doi:10.3762/bjoc.7.93
- photochemistry open an additional dimension for the control of chemical reactivity by enabling many, otherwise impossible, synthetic transformations, but this mode of activation also provides useful spatial and temporal control of chemical processes that are required to occur in the right place and at the right
- photochemistry is vital for unraveling the mechanistic scenarios that account for DNA cleavage by these compounds (Figure 3) [25]. As illustrated in Figure 3, multiple reaction pathways are potentially unlocked by the photoactivation of alkyne conjugates. In the past, we observed dramatic differences in
- potentially lead to a stronger pH-dependency on the photochemistry of the respective lysine conjugate, which is controlled by the protonation-gated intramolecular electron transfer from the α-amino group [25]. Interestingly, the meta-isomer has a noticeably longer singlet lifetime than the other two isomers
Intraannular photoreactions in pseudo-geminally substituted [2.2]paracyclophanes
Beilstein J. Org. Chem. 2011, 7, 658–667, doi:10.3762/bjoc.7.78
- crystal lattice locks the relative orientation of the substrate molecules or their photoreactive groups. If the orientation is favorable for reaction, reactivity increases. Unlike photochemistry in homogeneous solution, this often leads to highly selective formation of the photoproducts. Schmidt coined
- experimental elucidation of solid-state photochemistry. This showed that the supramolecular arrangement of molecules in the crystal plays a more important role for reaction control than the simple alignment of double bonds. Long-range molecular movements within crystals upon photochemical reaction and even
- topotactic single-crystal to single-crystal reactions were found, although the latter are rare. The subject has been comprehensively covered by recent reviews [6][7][8]. Reactions of inclusion complexes are a variation of the solid-state photochemistry topic [9]. Here, co-crystals of a host compound and the
The arene–alkene photocycloaddition
Beilstein J. Org. Chem. 2011, 7, 525–542, doi:10.3762/bjoc.7.61
- + 2] or meta, and the [4 + 2] or para photocycloaddition. This short review aims to demonstrate the synthetic power of these photocycloadditions. Keywords: benzene derivatives; cycloadditions; Diels–Alder; photochemistry; Introduction Photocycloadditions occur in a variety of modes [1]. The best
- photocycloaddition occurs selectively 1,3-exo to the tether. The stereochemistry on the trimethylsiloxy substituent was shown to have no influence on the photochemistry, but it helped to direct the olefin group towards the arene moiety. The linear and angular fused compounds were elaborated to give a common
- exposure to light but, depending on the substitution pattern, other reactive sites may be involved. Carbonyl groups are also known to undergo different types of photochemistry. Thus, benzophenones, acetophenones and benzaldehydes are not only used as sensitizers but can, under specific circumstances, also
Photoinduced electron-transfer chemistry of the bielectrophoric N-phthaloyl derivatives of the amino acids tyrosine, histidine and tryptophan
Beilstein J. Org. Chem. 2011, 7, 518–524, doi:10.3762/bjoc.7.60
- Axel G. Griesbeck Jorg Neudorfl Alan de Kiff University of Cologne, Department of Chemistry, Organic Chemistry, Greinstr. 4, D-50939 Köln, Germany; Fax: +49(221)470 5057 10.3762/bjoc.7.60 Abstract The photochemistry of phthalimide derivatives of the electron-rich amino acids tyrosine, histidine
- Norrish cleavage. The tryptophan derivative 10 is photochemically inert and shows preferential decarboxylation only when induced by intermolecular PET. Keywords: amino acids; decarboxylation; electron transfer; photochemistry; phthalimides; Introduction Phthalimides are versatile electron acceptors in
- +, electronically excited phthalimides are potent electron acceptors [2]. The rich photochemistry of this chromophore has recently been reviewed [3][4]. Intramolecular hydrogen abstraction is an archetype process for electronically excited carbonyl groups (Norrish type II reaction). The 1,4-biradicals formed by γ
Supramolecular FRET photocyclodimerization of anthracenecarboxylate with naphthalene-capped γ-cyclodextrin
Beilstein J. Org. Chem. 2011, 7, 290–297, doi:10.3762/bjoc.7.38
- γ-cyclodextrin; FRET sensitization; photochirogenesis; photocyclodimerization; Introduction Chiral photochemistry, often characterized by low optical yields, remains a great challenge for chemists [1][2][3]. This situation reflects primarily the difficulty in efficiently transferring the
- stereochemical information of the chiral source to the substrate in the electronically excited state. Thus, a supramolecular approach in chiral photochemistry could be a promising strategy for critically controlling the stereochemical outcome via intimate, long-lasting contacts with the photosubstrate through
Effects of anion complexation on the photoreactivity of bisureido- and bisthioureido-substituted dibenzobarrelene derivatives
Beilstein J. Org. Chem. 2011, 7, 278–289, doi:10.3762/bjoc.7.37
- formation of the dibenzosemibullvalene with moderate stereoselectivity (68:32 er). In contrast, the thioureido derivative showed no such effect upon complexation of chiral anions. Keywords: dibenzobarrelenes; dibenzosemibullvalenes; di-π-methane rearrangement; supramolecular photochemistry; (thio)urea
Photoinduced homolytic C–H activation in N-(4-homoadamantyl)phthalimide
Beilstein J. Org. Chem. 2011, 7, 270–277, doi:10.3762/bjoc.7.36
- for the abstraction. Keywords: homoadamantanes; photoinduced H-abstraction; phthalimides; Introduction Since the pioneering work of Ciamican and Paterno [1][2], the photochemistry of ketones has been intensively studied [3][4][5][6]. One important chemical pathway for the deactivation of ketones
- type II reaction [18][19][20]. The photochemistry of phthalimide derivatives is often similar to that of simple ketones [21][22][23][24][25][26][27][28][29][30][31][32][33]. For example, phthalimide derivatives in the electronically excited state abstract H-atoms from alcohols to give reduction
- (Scheme 1) [51]. The mechanism of the photoinduced domino reaction was investigated and it was found that it probably takes place from a higher excited triplet state or the singlet state [52]. Herein, we report the synthesis and photochemistry of a phthalimide derivative of homoadamantane 5. The research
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