Photoreactions of cyclic sulfite esters: Evidence for diradical intermediates

• Rick C. White,
• Benny E. Arney Jr. and
• Heiko Ihmels

Beilstein J. Org. Chem. 2012, 8, 1208–1212, doi:10.3762/bjoc.8.134

• loss of nitrogen from cyclic azo compounds is stepwise or concerted [6]. The photoextrusion of molecular nitrogen was employed also synthetically in the photoreaction of a benzothiadiazole to give an antiaromatic derivative of benzothiirene [7]. In another case, Griffin proposed carbene intermediates

• irradiation of the cyclic sulfite 8 for 3 h in acetonitrile gave phenyl acetaldehyde (3a), bibenzyl (4) and toluene (7) in Scheme 2; however, in contrast to the results of the photoreaction of the cyclic carbonate ester 1a under similar conditions, the oxirane 2a was not detected as a reaction product. The

• decarbonylation results in an alkyl radical. The latter reaction yields bibenzyl (4) and toluene (7) in the photoreaction of 8. It should be noted that the diradical BR2 may be formed also upon photoinduced ring-opening reaction of an intermediate oxirane 2a, which is not detectable in the reaction mixture

Recent advances towards azobenzene-based light-driven real-time information-transmitting materials

• Jaume García-Amorós and
• Dolores Velasco

Beilstein J. Org. Chem. 2012, 8, 1003–1017, doi:10.3762/bjoc.8.113

• applications are certainly azobenzenes. Azobenzene, a photochromic T-type system, exhibits a reversible isomerisation process between its trans and cis isomers of different stability. In this process, the photoreaction simply causes the rearrangement of the electronic and nuclear structure of the molecule

Discovery of practical production processes for arylsulfur pentafluorides and their higher homologues, bis- and tris(sulfur pentafluorides): Beginning of a new era of “super-trifluoromethyl” arene chemistry and its industry

• Teruo Umemoto,
• Lloyd M. Garrick and
• Norimichi Saito

Beilstein J. Org. Chem. 2012, 8, 461–471, doi:10.3762/bjoc.8.53

• pentafluoride). Photoreaction of HC≡CSF5 in the presence of SF5Cl gave phenyl-1,3,5-tris(sulfur pentafluoride), but in low yield (19%) [42]. All of the previous methods described above suffer from multiple drawbacks of low yields, the necessity of costly and dangerous fluoro-reagents, and the quite limited

Intraannular photoreactions in pseudo-geminally substituted [2.2]paracyclophanes

• Henning Hopf,
• Vitaly Raev and
• Peter G. Jones

Beilstein J. Org. Chem. 2011, 7, 658–667, doi:10.3762/bjoc.7.78

• on temperature. The geometry of zeolite cavities restricts conformation and orientation of included guests and their reaction partners and leads to more selective reactions. In the absence of any low-energy electronic states of the zeolite, photoreaction occurs only with the included guest. The

Supramolecular FRET photocyclodimerization of anthracenecarboxylate with naphthalene-capped γ-cyclodextrin

• Qian Wang,
• Cheng Yang,
• Gaku Fukuhara,
• Tadashi Mori,
• Yu Liu and
• Yoshihisa Inoue

Beilstein J. Org. Chem. 2011, 7, 290–297, doi:10.3762/bjoc.7.38

• within the CD cavity, minimizing the “contamination” from the achiral “outside” photoreaction, is responsible. FRET sensitization also enabled us to achieve the catalytic photocyclodimerization of AC with a sub-equivalent amount of chiral supramolecular host. Keywords: anthracenecarboxylic acid; capped

• non-covalent interactions in the ground state [4][5][6][7][8][9][10][11]. The geometrical and functional complementarity and the subsequent induced fit between chiral host and guest substrate should play a crucial role in determining the stereochemical fate of chiral photoreaction, and therefore the

• ) 3 are chiral (Scheme 1). This chiral photoreaction turned out to be an ideal benchmark system for exploring and comparing the performance of various chiral hosts, such as cyclodextrins (CDs), proteins and chiral hydrogen-bonding templates. γ-CD can significantly accelerate the photocyclodimerization

Effects of anion complexation on the photoreactivity of bisureido- and bisthioureido-substituted dibenzobarrelene derivatives

• Heiko Ihmels and
• Jia Luo

Beilstein J. Org. Chem. 2011, 7, 278–289, doi:10.3762/bjoc.7.37

• derivatives; Introduction The control of the selectivity of a photoreaction by supramolecular interactions has recently received much attention [1][2][3]. For example, chiral receptors have been employed that associate with photoreactive substrates, leading to a distinct preferential conformation of the

• spectroscopy with SMD as chiral shift reagent, as it turned out that this additive induces a significant separation of the protons of the enantiomers of 2h (Supporting Information File 1). The absolute configuration of the products was not determined. The photoreaction proceeded rapidly with full conversion in

• )-enantiomer of mandelate induced the same extent of stereoselectivity with the reverse ratio of products. For comparison, the photoreaction of dibenzobarrelene 1h was performed in the presence of other chiral anions, namely (R)-thiazolidine-4-carboxylate (RTZ), (S)-camphor-10-sulfonate (SCS), (R)-carnitine

Photoinduced homolytic C–H activation in N-(4-homoadamantyl)phthalimide

• Nikola Cindro,
• Margareta Horvat,
• Kata Mlinarić-Majerski,
• Axel G. Griesbeck and
• Nikola Basarić

Beilstein J. Org. Chem. 2011, 7, 270–277, doi:10.3762/bjoc.7.36

• ring closure to azetidinols and ring enlargement to azepinediones. High selectivity and high isolable yield of 6 in the photoreaction of 5 makes this photoinduced C–H activation useful in the synthesis of very complex derivatives with the homoadamantane skeleton with potential antiviral activity for

Formation of macrocyclic lactones in the Paternò–Büchi dimerization reaction

• Junya Arimura,
• Tsutomu Mizuta,
• Yoshikazu Hiraga and
• Manabu Abe

Beilstein J. Org. Chem. 2011, 7, 265–269, doi:10.3762/bjoc.7.35

• , although intramolecular cyclization products are known to be products in the photoreaction of 3-substituted furan derivatives [11][21]. Furan-2-carbaldehyde (3) was the only assignable product during the photochemical reaction, which was monitored by 1H NMR spectroscopy (Figure 2). The intermolecular

• Paternò–Büchi reaction product, i.e., C in Scheme 2, was also not observed in the photolysate. This result suggests that the intramolecular Paternò–Büchi reaction of C is faster than the first intermolecular Paternò–Büchi reaction of 1a. The photoreaction of 1b (R = Me) gave 2b and 3 in 25% and 18

• -pressure Hg lamp (300 W, hν > 290 nm) with a Pyrex filter. After 13 h, the solvent was removed in vacuo and dimethyl fumarate added as an internal standard. 1H NMR (500 MHz, CDCl3) was measured to determine the ratio of products. After the photoreaction, the residue was purified by repeated column

Synthesis of cationic dibenzosemibullvalene-based phase-transfer catalysts by di-π-methane rearrangements of pyrrolinium-annelated dibenzobarrelene derivatives

• Heiko Ihmels and
• Jia Luo

Beilstein J. Org. Chem. 2011, 7, 119–126, doi:10.3762/bjoc.7.17

• -reaction during the direct photolysis of compounds 2a–d, leading to the formation of complex reaction mixtures. The triplet-sensitized photoreaction of the dibenzobarrelene derivatives 2e,f, which carry two different alkyl substituents at the quaternary pyrrolidinium, gave two isomeric

• . However, further attempts to clarify this aspect or to optimize the conditions for sensitization were not made, because the photoreaction of 2g upon external sensitization by acetone showed that the products of the DPM rearrangement of 2g are formed only slowly in relatively low yield and cannot be

• . A solid-state photoreaction was also performed by the irradiation of a suspension of crystalline 2b-4 in diethyl ether. The solid products were dissolved and precipitated as perchlorate salts. Although the dibenzosemibullvalene 3b was formed (68%), 1H NMR spectroscopic analysis of the photolysate

Heavy atom effects in the Paternò–Büchi reaction of pyrimidine derivatives with 4,4’-disubstituted benzophenones

• Feng-Feng Kong,
• Jian-Bo Wang and
• Qin-Hua Song

Beilstein J. Org. Chem. 2011, 7, 113–118, doi:10.3762/bjoc.7.16

• . Photoproducts 2 and 3 have no significant absorption for light at above 290 nm. Hence, a secondary photolysis of the oxetane products (2 or 3) should not occur unless there is prolonged irradiation. Compositions in photoreaction mixture were quantified by 1H NMR spectroscopy (300 MHz) directly on the crude

• within 5%. The yield and the ratio of 2/3 at different reaction times in the Paternò–Büchi reaction of DMT with 1e (DMT:1e = 5 mM:5 mM, irradiation at 10 °C). Eyring plots for the photoreaction of DMT with compounds 1b–e. The Paternò–Büchi reaction of DMT/DMU with benzophenones to generate two

Anthracene functionalized terpyridines – synthesis and properties

• Falk Wehmeier and
• Jochen Mattay

Beilstein J. Org. Chem. 2010, 6, No. 54, doi:10.3762/bjoc.6.54

• blocks for photochromic supramolecular structures. A possible explanation for the observed irreversible photoreaction may be an unsymmetrical [4 + 4]-cycloaddition, connecting the anthracene moieties via the 1,4:9′,10′- instead of the 9,10:9′,10′-positions. The line-shape and the absorption increase for

A perfluorocyclopentene based diarylethene bearing two terpyridine moieties – synthesis, photochemical properties and influence of transition metal ions

• Falk Wehmeier and
• Jochen Mattay

Beilstein J. Org. Chem. 2010, 6, No. 53, doi:10.3762/bjoc.6.53

• band can be attributed to communication between the ruthenium nuclei. In this case communication is obviously reduced by the bridging photoreaction of the diarylethene [9]. On one hand this seems quite unexpected, since the extended π-system of the closed isomer 10aC should facilitate charge transfer

• inhibition nor any significant slowing of the photoreaction of the ligand was observed. Conclusion We have developed the synthesis of two highly fatigue resistant bis(terpyridinyl) diarylethenes by Suzuki cross coupling methods. The photochemical behavior of the free ligand 10a met our expectations regarding

• reversibility. It was shown that the presence of various transition metal ions significantly influences the photochromism of the bridging unit: While iron(II)-ions completely inhibit the photochromic reaction, cobalt(II) and nickel(II) appear to slow down the photoreaction considerably. Zinc(II)-ions, on the

Molecular recognition of organic ammonium ions in solution using synthetic receptors

• Andreas Späth and
• Burkhard König

Beilstein J. Org. Chem. 2010, 6, No. 32, doi:10.3762/bjoc.6.32

Synthesis of rigidified flavin–guanidinium ion conjugates and investigation of their photocatalytic properties

• Harald Schmaderer,
• Mouchumi Bhuyan and
• Burkhard König

Beilstein J. Org. Chem. 2009, 5, No. 26, doi:10.3762/bjoc.5.26

• show that 10 mol% of flavin 2, the same amount of tetraacetyl riboflavin (3) or compound 8 catalyze the photoreaction equally well. The guanidinium ion binding site of 1 and 2 does not lead to a more effective conversion. The intermolecular interaction of the guanidinium ion binding site of compound 2

Synthesis of novel photochromic pyrans via palladium- mediated reactions

• Christoph Böttcher,
• Gehad Zeyat,
• Saleh A. Ahmed,
• Elisabeth Irran,
• Thorben Cordes,
• Cord Elsner,
• Wolfgang Zinth and
• Karola Rueck-Braun

Beilstein J. Org. Chem. 2009, 5, No. 25, doi:10.3762/bjoc.5.25

• its “ring-opened” forms. The photoreaction was initiated by short light-pulses at 340 nm. The corresponding transient absorption changes (375–650 nm) as a function of the delay-time between pump and probe are shown in Figure 1a. An inspection of the data at early delay-times (0.2 ps) reveals a broad

Photosonochemical catalytic ring opening of α-epoxyketones

• Hamid R. Memarian and
• Ali Saffar-Teluri

Beilstein J. Org. Chem. 2007, 3, No. 2, doi:10.1186/1860-5397-3-2

• -2,4,6-triphenylpyridinium tetrafluoroborate (NBTPT) as photocatalyst in methanol. Sonication of these compounds in the presence of NBTPT did not result in the opening of epoxide ring, but the use of ultrasound increased the rate of photoreaction. Background The advantages of ultrasound-assisted