Improved efficiency of photo-induced synthetic reactions enabled by advanced photo flow technologies

Abstract

In this article, we discuss how effective photo-induced organic reactions became when applied evolving photo flow technologies through our experiences over these two last decades. We started with the flow update of traditional [2 + 2] cycloaddition using Mikroglas Dwell device as a flow reactor and a compact light source, such as blacklight, instead of a high-pressure mercury lamp. Then we examined Barton nitrite reaction using a photo flow reactor consisting of stainless-steel channels and a quartz glass top provided by DNS. Again the use of blacklight was successful. However, the energy profile of these reactions was improved further by the use of LED lights. We used a photo-flow set-up, consisting of stainless steel engraved microchannels covered by a quartz top (MiChS L-1) and a sodium lamp, for the isomerization of a fulleroid to PCBM. Photo-redox-catalyzed alkene alkylation proceeded within a shortened reaction time when the same photo flow reactor and white LED were used instead of a batch reactor. Photo-induced reductive 5-exo-dig radical cyclization and reduction of alkenyl halides proceeded smoothly, thanks to the combination of a photo flow reactor and low-pressure Hg lamp. We also applied flow technologies for photo-bromination and chlorination of C-H bonds. Photocatalytic oxidation of benzyl alcohol by molecular oxygen became quick when high-power LED irradiation was employed.

High-Speed Circulation Flow Platform Facilitating Practical Large-Scale Heterogeneous Photocatalysis

“…While conventional batch photochemical reactors remain the first choice for developing new reactions due to their low cost and ease of screening, operation, and reaction monitoring, continuous flow reactors are gaining increasing attention for scaling up photochemical reactions as a result of the Beer–Lambert law. − It is difficult to employ a dimension-enlarging strategy for scaling up reactions in conventional batch reactors due to the decay of light intensity and the increase of irradiation inhomogeneity . In contrast, a continuous microflow reactor can achieve uniform and effective light irradiation with narrow-diameter tubing or microchannels.…”

Methyl Oleate Synthesis by TiO2 Photocatalytic Esterification of Oleic Acid: Optimisation by Response Surface Quadratic Methodology, Reaction Kinetics and Thermodynamics

“…Scale‐up of heterogeneous photocatalytic processes remains challenging due to significant photon and mass transfer limitations [26] . Continuous‐flow conditions can generally improve the performances of photochemical transformations, [27] and have subsequently become widespread in synthetic photochemistry [28] . Recently, heterogeneous photocatalysis has been realized in an advanced meso‐scale flow reactor [29] .…”

“…[26] Continuous-flow conditions can generally improve the performances of photochemical transformations, [27] and have subsequently become widespread in synthetic photochemistry. [28] Recently, heterogeneous photocatalysis has been realized in an advanced meso-scale flow reactor. [29] Numbering-up of smaller reactors has furthermore been demonstrated for photocatalytic water treatment.…”

Accelerated nitroxide-mediated polymerization of styrene and butyl acrylate initiated by BlocBuilder MA using flow reactors

“…[13][14][15][16] We have long been involved in studies on using flow reactors in radical reactions versus batch processes, irrespective of whether they are thermally or photochemically induced. 17,18 In joint studies with the Studer group, we previously reported that (BA-St) di-block copolymers consisting of BA and St could be synthesized in a highly controlled manner using a continuous flow reactor and a designed TEMPO-type nitroxide. 19 We are now particularly interested in the industrial potential of using flow NMP reactions using an industrially available alkoxyamine, such as BlocBuilder MA (BB MA) which was developed and supplied by Arkema K.K., 20,21 especially as to whether the flow polymerization of BA-St di-block copolymer would be achieved in higher conversions.…”

“…In contrast, the addition of acetoin or α-hydroxy-γ-butyrolactone caused only a slight increase in the conversion. Among the active methylene compounds (Table 2, entries [15][16][17][18], malononitrile proved to be the most effective, giving an 89% conversion with Đ = 1.33 (Table 2, entry 18). Encouraged by the acceleration in reaction rate caused by adding acetol or malononitrile, we then investigated the amounts of additives needed for achieving optimal results.…”