Visible-light photooxygenation of α-terpinene in a falling film microreactor

Shvydkiv, Oksana; Jähnisch, Klaus; Steinfeldt, Norbert; Yavorskyy, Alexander; Oelgemöller, Michael

doi:10.1016/j.cattod.2017.11.009

Cited by 37 publications

(40 citation statements)

References 107 publications

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“…A transparent window allows irradiation for photochemical transformations. Applications of falling-film reactors in synthesis and catalysis are relatively rare, but a few recent studies on their use in photooxygenation reactions have been reported by Oelgemö ller and Rehm [39,40]. These reactors are, interestingly, also suitable for heterogeneous catalysis.…”

Section: Trends In Chemistrymentioning

confidence: 99%

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: Trends In Chemistrymentioning

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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“…An example by Oelgemöller and coworkers [22] demonstrates a falling film reactor set-up to bring about the effective photooxygenation of α-terpinene in the presence of Rose Bengal to generate ascaridole ( Figure 1). More recently, the Corning reactor system that is based on irradiated reactor plates has gained popularity as it allows one to effectively perform continuous photochemical reactions at various scales.…”

Section: Reactor Design and Technologymentioning

confidence: 99%

Continuous Flow Photochemistry for the Preparation of Bioactive Molecules

2020

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The last decade has witnessed a remarkable development towards improved and new photochemical transformations in response to greener and more sustainable chemical synthesis needs. Additionally, the availability of modern continuous flow reactors has enabled widespread applications in view of more streamlined and custom designed flow processes. In this focused review article, we wish to evaluate the standing of the field of continuous flow photochemistry with a specific emphasis on the generation of bioactive entities, including natural products, drugs and their precursors. To this end we highlight key developments in this field that have contributed to the progress achieved to date. Dedicated sections present the variety of suitable reactor designs and set-ups available; a short discussion on the relevance of greener and more sustainable approaches; and selected key applications in the area of bioactive structures. A final section outlines remaining challenges and areas that will benefit from further developments in this fast-moving area. It is hoped that this report provides a valuable update on this important field of synthetic chemistry which may fuel developments in the future.

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“…A possible way to circumvent this in microreactors might be by the addition of an inert carrier phase in which the precipitated FDCA particles are dispersed, preventing them from interacting with the microreactor wall or solid catalysts. [292][293][294][295] Oxygenated monoterpenes are promising building blocks for the synthesis of pharmaceuticals, flavorants and fragrances. Some research has been done recently on the oxidation of HMF to FDCA using ionic liquids in which FDCA dissolves well, [287,288] however, the application of ionic liquids for industrial production is not economically feasible yet.…”

Section: Opportunitiesmentioning

confidence: 99%

“…[291] Photocatalytic oxidation has been already conducted in microreactors for the oxygenation of biomass derivatives (e. g., monoterpenes derived from plants and in the singlet-oxygen oxidation of HMF to H 2 MF). [292][293][294][295] Oxygenated monoterpenes are promising building blocks for the synthesis of pharmaceuticals, flavorants and fragrances. [8] The oxidation of monoterpenes is industrially unfavorable as it requires long residence times and often a low product selectivity is obtained.…”

Section: Opportunitiesmentioning

confidence: 99%

Catalytic Transformation of Biomass Derivatives to Value‐Added Chemicals and Fuels in Continuous Flow Microreactors

2019

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Biomass as a renewable and abundantly available carbon source is a promising alternative to fossil resources for the production of chemicals and fuels. The development of biobased chemistry, along with catalyst design, has received much research attention over recent years. However, dedicated reactor concepts for the conversion of biomass and its derivatives are a relatively new research field. Continuous flow microreactors are a promising tool for process intensification, especially for reactions in multiphase systems. In this work, the potential of microreactors for the catalytic conversion of biomass derivatives to value-added chemicals and fuels is critically reviewed. Emphases are laid on the biphasic synthesis of furans from sugars, oxidation and hydrogenation of biomass derivatives. Microreactor processing has been shown capable of improving the efficiency of many biobased reactions, due to the transport intensification and a fine control over the process. Microreactors are expected to contribute in accelerating the technological development of biomass conversion and have a promising potential for industrial application in this area.

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Visible-light photooxygenation of α-terpinene in a falling film microreactor

Cited by 37 publications

References 107 publications

Flow Photochemistry: Shine Some Light on Those Tubes!

Flow Photochemistry: Shine Some Light on Those Tubes!

Continuous Flow Photochemistry for the Preparation of Bioactive Molecules

Catalytic Transformation of Biomass Derivatives to Value‐Added Chemicals and Fuels in Continuous Flow Microreactors

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