Microphotochemistry - a new resources efficient synthesis tool approach

Microphotochemistry, i.e. photochemistry in microstructured reactors, is a novel research area of the 21st century. It combines established techniques in organic photochemistry and continuous flow microsystem engineering with advances in light technology. This research work aimed to develop a novel resource- and energy-efficient approach in synthetic chemistry and to demonstrate that microflow-photochemistry can serve as a compact, rapid and resource efficient R&D tool. A series of homogeneous and heterogeneous photoreactions have been studied in microreactors to evaluate the potential of microphotochemistry. A range of acetonesensitized photodecarboxylation reactions involving phthalimides was investigated in commercially available microreactor dwell device and a number of isopropanol additions to furanones were studied in newly designed within the project LED-driven microchip. All results were compared to analogous experiments in conventional Rayonet reactor. In all cases examined, the reactions performed in the chosen microreactors gave higher conversions or yields. This finding was explained by the generated data of light penetration, irradiated surface-to-volume ratio, energy efficiency and space-time yield. The numbers achieved for continuous flow systems were notably higher compared to the conventional setup. This finding nicely proved superiority of microphotochemistry concept. Another commercially available device falling film microreactor was successfully adapted for the photooxygenation of -terpinene and new safer methodology have been developed for the synthesis of potentially explosive endoperoxide ascaridole. Major disadvantages of commercially available microreactors are, however, the fixed length of the reaction channel and the single-channel design. Although numbering-up can be achieved using an array of microreactors, which required significant costs investment. Flexible PTFE capillaries represent a cost-efficient alternative. Thus a simple continuous microflow dual-capillary reactor and its optimised version multimicrocapillary tower were developed. The tower design enables parallel operation of 10 experiments and it was successfully tested for reaction optimization, library synthesis and scale-up. The multi-capillary design may be easily transferred to other microflow applications such as parallel testing of biologically active compounds, process modeling, in situ analysis and combinatorial chemistry. Consequently, micro-photochemistry may serve as a compact, rapid and resource efficient R&D tool and opens new approaches for synthetic chemistry

Visible-Light Photoredox Catalysis in Flow

Photoredox catalysis: A variety of organic transformations mediated by visible-light-active photoredox catalysts have been conducted in a photochemical flow reactor. The reactor design is very simple and can be easily implemented in any laboratory (see picture). In addition, this reactor afforded a marked increase in the reaction rate compared to those observed in typical batch (round bottom flask) reactors.National Science Foundation (U.S.) (Grant CHE-1056568)National Institutes of Health (U.S.) (NIGMS Grant R01-GM096129)Alfred P. Sloan FoundationAmgen Inc.Boehringer Ingelheim PharmaceuticalsAmgen Inc. (Graduate Fellowship)NMR (CHE-0619339)MS (CHE-0443618

A laboratory-scale annular continuous flow reactor for UV photochemistry using excimer lamps for discrete wavelength excitation and its use in a wavelength study of a photodecarboxlyative cyclisation

This paper describes a new annular reactor for continuous UV photochemistry, which uses easily interchangeable excimer lamps of different wavelengths. The reactor has narrow clearance to form thin films of material for efficient irradiation of molecules. Its use is demonstrated by investigating the effect of discrete wavelength lamps (222, 282 and 308 nm) on the reaction of potassium N-phthalimidobutanoate 1. The ability of the reactor to be integrated into multistep processes is illustrated by combining it with an Amberlyst scavenger and a solid acid catalyst, NbOPO4, to access a second product 3 that is obtained in a single telescoped process. The tricyclic scaffold in 3 is a motif found in several biologically active compounds and has possibilities as a synthon for new pharmaceutical products

Recent advances in microflow photochemistry

This review summarizes recent advances in microflow photochemical technologies and transformations. The portfolio of reactions comprises homogeneous and heterogeneous types, among them photoadditions, photorearrangements, photoreductions, photodecarboxylations, photooxygenations and photochlorinations. While microflow photochemistry is most commonly employed as a micro-scale synthesis tool, scale-up and technical production processes have already been developed

Microphotochemistry: photochemical synthesis in microstructured flow reactors

[Extract] Over the last decades, microtechnology has received a great deal of attention. Its application rapidly grows in many areas, as evident, for example, in electronics and engineering. The development of microstructured devices for chemical reactions was observed only within the last 10 years. Miniaturization of chemical reactors offers many practical advantages of relevance to the pharmaceutical and fine chemicals industry. Also, the possibility of preparing chemicals in the required volume at the point of use neglects the need to store and transport hazardous materials. The small scales of microreactions make them additionally advantageous for green chemistry. Since light is regarded as a "clean reagent," organic photochemistry can Iikewise serve as a green synthetic method. The potential of organic photochemistry as a powerful synthesis mEthod is furthermore well documented, and a number of elegant chemo- and enantioselective transformations with high chemical and quantum yields have been realized. The combination of microtechnology and photochemistry, that is, microphotochemistry, thus represents a promising and appealing new concept (Figure 3.1)

Microreactortechnology: Real-Time Flow Measurements in Organic Synthesis

With the commercial availability of integrated microreactor systems, the numbers of chemical processes that are performed nowadays in a continuous flow is growing rapidly. The control over mixing efficiency and homogeneous heating in these reactors allows industrial scale production that was often hampered by the use of large amounts of hazardous chemicals. Accurate actuation and in line measurements of the flows, to have a better control over the chemical reaction, is of added value for increasing reproducibility and a safe production

Flow photochemistry – a GREEN Technology with a bright future: μ-photochemistry - a new resources-efficient synthesis tool

This report summarizes the results of the 'μ-Photochemistry a New Resources Synthesis Tool' project funded by the Irish Environmental Agency (EPA).\ud \ud Microphotochemistry is a novel research area of the twenty-first century that arises from significant progress in micro- and nanotechnologies. Microphotochemistry combines established techniques in organic photochemistry and continuous flow microsystem engineering with advances in light technology. Microphotochemistry can be considered to be an environmentally conscious methodology, contributing\ud to the rapidly expanding field of 'green chemistry', by reducing the volume of waste, improving energy efficiency and product selectivity

From 'Lab & Light on a Chip' to parallel microflow photochemistry

Continuous-flow microreactors offer major advantages for photochemical applications. This mini-review summarizes the technological development of microflow devices in the Applied and Green Photochemistry Group at James Cook University, and its associates, from fixed microchips for microscale synthesis to flexible multicapillary systems for parallel photochemistry. Whereas the enclosed microchip offered high space–time-yields, the open capillary-type reactor showed a greater potential for further modifications. Consequently, a 10-microcapillary reactor was constructed and used successfully for process optimization, reproducibility studies, scale-up, and library synthesis. To demonstrate the superiority of microflow photochemistry over conventional batch processes, the reactors were systematically evaluated using alcohol additions to furanones as model reactions. In all cases, the microreactor systems furnished faster conversions, improved product qualities, and higher yields. UVC-induced [2+2] cycloadditions of furanone with alkenes were exemplarily examined in a capillary reactor, thus proving the broad applicability of this reactor type