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

• is multiplicity-dependent: The direct irradiation of 1a leads to the dibenzocyclooctatetraene 3a in a singlet reaction that occurs via an initial [2 + 2] cycloaddition followed by a [4 + 2] retro-Diels–Alder reaction [27][28][29][30]. In the presence of a triplet sensitizer, e.g., acetone or

• (trifluoromethyl)phenyl substituents. Notably, not even the commonly employed sensitizer acetone is capable of inducing the DPM rearrangement of 1i. Considering the different photophysical and photochemical properties of the carbonyl and thiocarbonyl chromophores [49], it may be that a similar difference exists

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

• unreacted 5 was recovered. This finding is in accordance with acetone acting as a triplet sensitizer and the anticipated triplet state reactivity of the phthalimide in the H-abstraction reactions. Furthermore, the addition of H2O as a protic solvent also increased the reactivity of the phthalimide, based on

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

• presence of an appropriate sensitizer, such as acetone or benzophenone, dibenzobarrelene (DBB) rearranges to dibenzosemibullvalene (DBS), whereas the direct excitation leads to dibenzocyclooctene (DBC) through the singlet excited-state (Scheme 1) [4][5][7]. The DPM photorearrangement of dibenzobarrelene

• -sensitizing functionality attached, namely the benzophenone unit. Although in acetone the dibenzobarrelene 2g underwent a DPM rearrangement with full conversion (Scheme 4), the irradiation of 2g in water or acetonitrile solution in the absence of an external sensitizer only induced a relatively low conversion

• separated. Since the covalent attachment of a sensitizer unit to the dibenzobarrelene chromophore did not induce the desired triplet sensitization, the ionic auxiliary strategy [19] was applied to achieve triplet-sensitization in the solid-state, i.e., the sensitizer was introduced as counter anion. For

Conjugated polymers containing diketopyrrolopyrrole units in the main chain

• Bernd Tieke,
• A. Raman Rabindranath,
• Kai Zhang and
• Yu Zhu

Beilstein J. Org. Chem. 2010, 6, 830–845, doi:10.3762/bjoc.6.92

• a conjugated main chain and nonlinear optically active (nlo) chromophores in the side chain. DPP was incorporated in the polymers as a sensitizer for charge carrier generation. Some years later, Eldin and coworkers described DPP-containing polymers obtained by radical polymerization of bis-acryloyl

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

• presence of the anions did not induce significant changes of the emission properties suggesting affinity constants smaller than 103 L/mol. Photo Diels–Alder reactions in the presence of a sensitizer and light have been described [59][60][61][62][63][64]. Therefore flavins 1 and 2 were tested as catalyst

Synthesis of 2,3,6,7-tetrabromoanthracene

• Christian Schäfer,
• Friederike Herrmann and
• Jochen Mattay

Beilstein J. Org. Chem. 2008, 4, No. 41, doi:10.3762/bjoc.4.41

• , such as 2,3,6,7-tetradehydroanthracene (for constructing polycyclic aromatic hydrocarbons [13][14]) and 2,6,9,10-tetracyanoanthracene (which has been used as sensitizer for organic photoconductors [15]). Results and Discussion In Scheme 1, the reaction pathway is shown, starting from benzene, which is