A Small-Footprint, High-Capacity Flow Reactor for UV Photochemical Synthesis on the Kilogram Scale

Elliott, Luke D.; Berry, Michael S.; Harji, Bashir H.; Klauber, David J.; Leonard, John; Booker‐Milburn, Kevin I.

doi:10.1021/acs.oprd.6b00277

Cited by 119 publications

(105 citation statements)

References 54 publications

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“…A limitation of this method is observed when tubing made of perfluorinated polymers is used under UV irradiation. This type of tubing is commonly used due to its flexibility and transparency, but prolonged exposure to UV might result in fouling (in turn lowering the transparency) [84][85][86] and/or mechanical damage [84], ultimately resulting in reaction inhibition or reactor replacement.…”

Section: Scale-up Strategies and Designsmentioning

confidence: 99%

“…Other reactor designs specific for large-scale photoreactions have been reported in recent years. To solve the limitations associated with UV irradiation on fluorinated polymers, Booker-Milburn and coworkers designed a quartz-based compact flow reactor (the Firefly) able to process liters of solution and run continuously for long times, giving productivities of 21-335 g h À1 for various UV-promoted cyclization reactions ( Figure 5D) [84]. Another interesting continuous photoreactor design was reported by AbbVie scientists for a dual-catalytic Csp 2 -Csp 3 decarboxylative coupling.…”

Section: Scale-up Strategies and Designsmentioning

confidence: 99%

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Flow Photochemistry: Shine Some Light on Those Tubes!

Sambiagio

Noël

2020

Trends in Chemistry

313

223

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Continuous-flow chemistry has recently attracted significant interest from chemists in both academia and industry working in different disciplines and from different backgrounds. Flow methods are now being used in reaction discovery/methodology, in scale-up and production, and for rapid screening and optimization. Photochemical processes are currently an important research field in the scientific community and the recent exploitation of flow methods for these methodologies has made clear the advantages of flow chemistry and its importance in modern chemistry and technology worldwide. This review highlights the most important features of continuous-flow technology applied to photochemical processes and provides a general perspective on this rapidly evolving research field. Microflow Technology and Photochemistry: A Perfect MatchThe use of light to promote chemical reactions has been exploited since the 18th century, but only recently a resurgence has been observed in synthetic organic chemistry, in particular due to the development of visible-light photoredox catalysis [1-5]. All transformations involving light (e.g., Figure 1A-D) must consider, besides classical chemical parameters (i.e., reaction conditions), the photophysical aspects of the sensitizer (see Glossary)/photocatalyst (when used), and the reactor design. The latter, although often neglected by chemists, is a critical aspect for the outcome of the studied chemical transformation. This includes, for example, the size, shape, and material of the reaction vessel, the characteristics and positioning of the light source(s), and heat-transfer properties, particularly when high-intensity lamps are used [6,7]. The engineering and technological aspects of photochemical processes are often at the basis of the irreproducibility and non-scalability of such transformations.According to the Beer-Lambert law, light transmittance decreases exponentially with the distance from the light source ( Figure 1F). For a standard batch reactor (diameter at least in the centimeter range), light intensity decreases considerably from the flask walls to the middle of the reaction mixture, resulting in slow reactions and nonhomogeneous irradiation of the reaction mixture. Performing photochemical reactions in microchannels (ID < 1 mm) allows a higher and more homogeneous photon flux, resulting in shorter reaction times and consequently less side-product formation due to over-irradiation, often observed in batch [8,9]. Another advantage of microflow chemistry, correlated with the large surface:volume ratio, is improved heat and mass transfer, with the possibility to perform mass-transfer-limited multiphasic reactions efficiently [10]. Reactive chemicals and intermediates can be handled more safely in flow than in batch, as no accumulation of dangerous components occurs within the confined reactor volume due to the continuous nature of the process. Together, these result in often faster, safer, and higher-yielding reactions, with the possibility to perform reactions under condition...

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Section: Scale-up Strategies and Designsmentioning

confidence: 99%

Section: Scale-up Strategies and Designsmentioning

confidence: 99%

Flow Photochemistry: Shine Some Light on Those Tubes!

Sambiagio

Noël

2020

Trends in Chemistry

313

223

View full text Add to dashboard Cite

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“…Comparison of STY with other flow systems is difficult if not impossible due to lack of benchmark systems. However, for thio‐ether 3 , for example, a productivity of 0.468 kg per day in a 2 mL reactor system, using a low‐powered irradiation source (∼7 W radiant power), once more demonstrates the scalability potential of UV‐induced photo‐flow chemistry . In this respect, a word is added in favour of the irradiation system.…”

Section: Resultsmentioning

confidence: 99%

Thiol−Ene Coupling in a Continuous Photo‐Flow Regime

Janssens¹,

Debrouwer²,

Aken³

et al. 2018

ChemPhotoChem

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Photoinitiated thiol−ene chemistry is a promising technique for use in chemical synthesis and related sciences. In view of scaling, the process was successfully transferred to a continuous flow regime with compelling results in terms of selectivity, efficiency, and productivity. A series of selected thiols and enes were reacted using 2,2‐dimethoxy‐2‐phenylacetophenone as radical initiator to respond to the 365 nm UV‐LED source. Process parameters were evaluated and chemical cross‐reactivity of the different substrates was assessed. Optimization of conditions gave high productivity of the thio‐ether resulting from the model reaction between benzyl thiol and 1‐decene when performed under neat conditions. The robustness of this method was demonstrated by running it under continuous operation for an extended period of time, with product output reaching constant yields of 90–92 % as soon as the steady‐state regime was installed. The corresponding space–time yield was 9.75 kg l−1 h−1, an impressive value that further demonstrates scale‐up potential.

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“…While there have been significant advances in developing flow reactors for large scale photochemical reactions [40-42], there are still few available options which could be applied to challenging reactions requiring low temperatures and are simple, affordable, and modular. We designed and built a novel flow photoreactor that would enable UV irradiation >300 nm while maintaining a low temperature for the photocycloaddition (Figure 2 A).…”

Section: Resultsmentioning

confidence: 99%