Tsuneo Kashiwagi

In situ electrogeneration of o-benzoquinone and high yield reaction with benzenethiols in a microflow system.

We have successfully demonstrated that a microflow reactor is extremely useful in controlling reactions involving an unstable o-benzoquinone. The key features of the method are an effective o-benzoquinone generation and its rapid use for the following reaction without decomposition in a microflow system.

An anodic aromatic C,C cross-coupling reaction using parallel laminar flow mode in a flow microreactor

We have successfully demonstrated an efficient anodic aromatic C,C cross-coupling reaction using parallel laminar flow mode in a two-inlet flow microreactor. The model reaction proceeded effectively even in single flow-through operations and the desired cross-coupling product was obtained in much higher current yields compared to the reaction in a conventional batch type cell.

Product selectivity control induced by using liquid–liquid parallel laminar flow in a microreactor

Product selectivity control based on a liquid-liquid parallel laminar flow has been successfully demonstrated by using a microreactor. Our electrochemical microreactor system enables regioselective cross-coupling reaction of aldehyde with allylic chloride via chemoselective cathodic reduction of substrate by the combined use of suitable flow mode and corresponding cathode material. The formation of liquid-liquid parallel laminar flow in the microreactor was supported by the estimation of benzaldehyde diffusion coefficient and computational fluid dynamics simulation. The diffusion coefficient for benzaldehyde in Bu(4)NClO(4)-HMPA medium was determined to be 1.32 × 10(-7) cm(2) s(-1) by electrochemical measurements, and the flow simulation using this value revealed the formation of clear concentration gradient of benzaldehyde in the microreactor channel over a specific channel length. In addition, the necessity of the liquid-liquid parallel laminar flow was confirmed by flow mode experiments.

Continuous In Situ Electrogeneration of o-Benzoquinone in Microreactor: Application to High Yield Reaction with Benzenethiols

We have successfully demonstrated that a microflow reactor is extremely useful in controlling reactions involving an unstable o-benzoquinone. As a model reaction, Michael addition reaction between o-benzoquinone generated from electrochemical oxidation of catechol and benzenethiols was employed. This reaction system enables selective oxidation of catechol avoiding the oxidation of benzenethiol, although these oxidation potentials are close to each other. The examination of several reaction conditions indicated that the key features of the method are an effective o-benzoquinone generation and its rapid use for the following reaction without decomposition in a microflow system. In addition, cyclic voltammetry measurements elucidated that catechol concentration and selection of anode material were crucial factors for effective o-quinone generation.

Continuous in situ electrogenaration of a 2-pyrrolidone anion in a microreactor: application to highly efficient monoalkylation of methyl phenylacetate

We have successfully demonstrated effective generation of an electrogenerated base (EGB) such as the 2-pyrrolidone anion and its rapid use for the following alkylation reaction in a flow microreactor system without the need for severe reaction conditions. The key feature of the method is effective and selective preparation of monoalkylated products.

Cathodic Aromatic C,C Cross-Coupling Reaction via Single Electron Transfer Pathway

We have successfully developed a novel cathodic cross-coupling reaction of aryl halides with arenes. Utilization of the cathodic single electron transfer (SET) mechanism for activation of aryl halides enables the cross-coupling reaction to proceed without the need for any transition metal catalysts or single electron donors in a mild condition. The SET from a cathode to an aryl halide initiates a radical chain by giving an anion radical of the aryl halide. The following propagation cycle also consists entirely of anion radical intermediates.