Authors:Akihiko Ouchi, Takeshi Hyugano, Masayuki Kaneda, Toshiaki Suzuki and Chuanxiang Liu
A microchannel reactor was used for suppressing undesirable side reactions in a photochemical reaction. A two-step photolysis, flavone (1) → flavanone (2) → salicylic acid (3b), was conducted in a microchannel reactor using a two-phase photolysis, that is, 1 and NaBH4 were dissolved in immiscible H2O and hexane, respectively, and photolyses were conducted at their interface. The two-step photolysis product 3b was obtained as a major product. In contrast, photolysis in homogeneous EtOH solution gave flavanol (4) as a major product. The thermal side reaction 2 → 4 was suppressed completely by the interface photolysis, and a greater than 25-fold increase was observed in the selectivity of 3b.