Organic reactions in systems containing two immiscible liquid phases appear in a number of important applications. Reaction between two substances located in different phases of a mixture is often inhibited because of the inability of reagents to come together. Traditionally, phase-transfer catalysis (PTC) is commonly used to enhance reaction rates, making feasible a wide variety of synthetic reactions not possible in a single phase. The most common arrangement for PTC involves the transport of a water-soluble reactant into an immiscible organic solvent or into the interface of two immiscible solvents with an appropriate hydrophobic phase transfer catalyst. However, one cannot avoid the problems by using phase transfer catalyst, such as cost, thermal instability, and separation/recycling. Therefore, methodology that avoids using phase transfer catalyst but can still enable the two-phase reaction to occur quickly might be a significant advance. Because reactions are carried out between immiscible phases, the nature of the interface and the physical properties of the reacting compounds at the interface become very important in promoting the desired reaction rate at a satisfactory level. Methods that can enlarge the interfacial contact area between the two phases should effectively enable better mass transfer. In this work, we provide a strategy to perform superfast two-phase reactions in microdroplets without using a phase transfer catalyst. Bulk liquid-liquid system was dispersed as small droplets in a manner such that interfacial area between the two phases is increased by many orders of magnitude. Stevens oxidation without using phase transfer catalyst was applied here as a proof of concept. Various alcohols can be oxidized to the corresponding aldehydes within milliseconds. A preparative scale experiment was also performed to demonstrate the practical utility of the present method.<br/>

Superfast two-phase reactions in microdroplets without the use of phase transfer catalyst

253rd National Meeting (2017)

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