Aggregation Effects in Visible-Light Flavin Photocatalysts: Synthesis, Structure, and Catalytic Activity of 10-Arylflavins

作者：Dadova Jitka; Kuemmel Susanne; Feldmeier Christian; Cibulkova Jana; Pazout Richard; Maixner Jaroslav; Gschwind Ruth M; Koenig Burkhard; Cibulka Radek^*

来源：Chemistry - A European Journal, 2013, 19(3): 1066-1075.

DOI：10.1002/chem.201202488

• aggregation
• flavins
• noncovalent interactions
• organocatalysis
• oxidation
• photocatalysis

A series of 10-arylflavins (10-phenyl-, 10-(2%26apos;,6%26apos;-dimethylphenyl)-, 10-(2%26apos;,6%26apos;-diethylphenyl)-, 10-(2%26apos;,6%26apos;-diisopropylphenyl)-, 10-(2%26apos;-tert-butylphenyl)-, and 10-(2%26apos;,6%26apos;-dimethylphenyl)-3-methylisoalloxazine (2?af)) was prepared as potentially nonaggregating flavin photocatalysts. The investigation of their structures in the crystalline phase combined with 1H-DOSY NMR spectroscopic experiments in CD3CN, CD3CN/D2O (1:1), and D2O confirm the decreased ability of 10-arylflavins 2 to form aggregates relative to tetra-O-acetyl riboflavin (1). 10-Arylflavins 2?ad do not interact by pp interactions, which are restricted by the 10-phenyl ring oriented perpendicularly to the isoalloxazine skeleton. On the other hand, N3?H...O hydrogen bonds were detected in their crystal structures. In the structure of 10-aryl-3-methylflavin (2?f) with a substituted N3 position, weak C?H...O bonds and weak pp interactions were found. 10-Arylflavins 2 were tested as photoredox catalysts for the aerial oxidation of 4-methoxybenzyl alcohol to the corresponding aldehyde (model reaction), thus showing higher efficiency relative to 1. The quantum yields of 4-methoxybenzyl alcohol oxidation reactions mediated by arylflavins 2 were higher by almost one order of magnitude relative to values in the presence of 1.

• 出版日期2013-1