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

• catalytic efficacy, flavin derivatives bearing a guanidinium ion as oxoanion binding site were prepared. Chromophore and substrate binding site are linked by a rigid Kemp’s acid structure. The molecular structure of the new flavins was confirmed by an X-ray structure analysis and their photocatalytic

• bonding site for oxoanions or carbonyl groups [45][46][47][48][49]. The structure of the new flavins was determined in solid state and in solution and their photocatalytic properties were tested. Results and Discussion Synthesis The synthesis of the potential photocatalysts 1 and 2, consisting of the

• bonds [54][55][56][57][58] and in solution the flavin chromophore is expected to rotate freely around the C–C single bonds of the ethane linker. Photocatalytic reactions Compounds 1 and 2 were tested as photocatalysts in three different reactions and their performance was compared to tetraacetyl

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

• carbonyl compounds [43][44][45][46][47][48][49][50] or by nucleophilic attack of appropriate reagents. [36][39][51] Recently, we have reported on the photocatalytic ring opening of α-epoxyketones 1a-f and 2,4,6-triphenylpyrilium tetrafluoroborate (TPT) as photocatalyst in methanol, [37] cyclohexanone, [38

• simultaneous irradiation of ultrasound and UV-light for catalytic ring opening of α-epoxyketones 1a-f in the presence of this photocatalyst in methanol. The main goal of the present work was to elucidate the effect of both irradiation sources separately or together on the rate of photocatalytic ring opening of

• of photocatalytic ring opening of α-epoxyketones 1b, 1d and 1f, the same substituents on the phenyl ring of the benzoyl group (1c and 1e) have a smaller effect. In the cases of 1b and 1d, the ratios of the diastereomeric photoproducts are inversed. We have proposed the involvement of three different