Microflow photo-radical reaction using a compact light source: application to the Barton reaction leading to a key intermediate for myriceric acid A

Sugimoto, Atsushi; Fukuyama, Takahide; Sumino, Yukihito; Takagi, Makoto; Ryu, Ilhyong

doi:10.1016/j.tet.2008.12.063

Cited by 93 publications

(51 citation statements)

References 46 publications

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“…Energy efficiency is one parameter for evaluating apparatus performance. As some papers have suggested, energy efficiency was determined by the reaction conversion per W h (Lamp power × irradiation time) [27,28]. In our experiment, only one of the 6 UV-LEDs used in the microreactor was used in the batch.…”

Section: Apparatus Comparisonmentioning

confidence: 99%

Diastereodifferentiating [2+2] photocycloaddition of chiral cyclohexenone carboxylates with cyclopentene by a microreactor

Terao

Nishiyama

Aida

et al. 2012

Journal of Photochemistry and Photobiology A: Chemistry

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Section: Apparatus Comparisonmentioning

confidence: 99%

Diastereodifferentiating [2+2] photocycloaddition of chiral cyclohexenone carboxylates with cyclopentene by a microreactor

Terao

Nishiyama

Aida

et al. 2012

Journal of Photochemistry and Photobiology A: Chemistry

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“…In this research, we aimed to use the low-power lamp and improve the other influential parameters instead. Also, Sugimoto et al [21] has thoroughly studied the application of the Barton reaction in microreactors and the effect of different light sources. They showed that, in their case, an ultraviolet (UV)-LED lamp (1.7 W) is more efficient than a 300-W Hg lamp.…”

Section: Resultsmentioning

confidence: 99%

Photo-Claisen Rearrangement of Allyl Phenyl Ether in Microflow: Influence of Phenyl Core Substituents and Vision on Orthogonality

2016

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We converted diverse commercial meta-substituted phenols to the allyl-substituted precursors via nucleophilic substitution using batch technology to allow processing these in microflow by means of the photo-Claisen rearrangement. The latter process is researched on its own, as detailed below, and also prepares the ground for a fully continuous two-step microflow synthesis, as outlined above. It is known that batch processing of electronically deactivated phenols (e.g., bearing a cyano or nitro group) has several orders of magnitude lower reactivity than their parental counterparts [1]. Thus, we here explore if the high quantum yield of microflow, yet at very short residence time, is sufficient to activate the deactivated molecules. In addition, the realization of a true orthogonal two-step flow synthesis can open the door to a large synthetic scope of our approach and possibly overcome limitations due to missing orthogonality of our previously reported thermal approach of combined nucleophilic substitution-Claisen rearrangement in microflow. Consequently, we make for our photo microflow approach an orthogonality check, as previously reported for the thermal approach, and compare both. To get a broader picture, we have investigated some major parametric sensitivities such as the irradiation intensity, the choice of solvent, the reactant concentration, and, most notably, the influence of the substitution pattern. The irradiation intensity was varied by increasing distance between a lamp and the microflow capillary. In addition, the normal photoClaisen microflow process (at room temperature) is compared to a high-temperature photo-Claisen microflow process, to check the potential of such novel process window [2]. This is difficult to realize in batch, as the combination of strong ultraviolet (UV) irradiation and high temperature causes a high hazard potential. Yet, under microflow, this can be safely handled.

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“…Scale-up in these systems can be achieved through numbering-up using an array of microreactors. 54 The open dual microcapillary reactor (III) allows the investigation of two different reaction mixtures, which makes it interesting for comparison and optimization studies. In an extension of this design concept, a 10-capillary twin-tower has been constructed and tested successfully for typical R&D applications such as process optimization and library synthesis.…”

Section: 50mentioning

confidence: 99%

Green Photochemical Processes and Technologies for Research & Development, Scale‐up and Chemical Production

Oelgemöller

2014

J Chinese Chemical Soc

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Photochemistry is often viewed as a green chemical method since photons are regarded as a 'clean and traceless reagent'. Despite this, photochemical transformations generally suffer from a variety of 'non-green' drawbacks that have prevented their widespread adaptation in chemical manufacturing. These include the necessity for hazardous solvents, low quantum yields of photochemical transformations, high energy demands of traditional lamps and the need for high dilution due to the low penetration of light into the reaction mixture. As a result, photochemical operations generate large volumes of hazardous solvent waste, demand prolonged irradiation times and require high energy inputs. This highlight article shows recent examples of green photochemical processes and technologies that overcome these limitations. These include photodecarboxylations in water matrices with high quantum yields in an advanced 308-nm excimer falling film reactor, solar photooxygenations utilizing concentrated sunlight generated in a parabolic trough loop and photosensitized additions in resource-efficient microreactors under continuous flow conditions. The results show that photochemistry can be implemented as a truly green methodology across the entire chemical process spectrum from early R&D to scale-up and subsequently production.

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Microflow photo-radical reaction using a compact light source: application to the Barton reaction leading to a key intermediate for myriceric acid A

Cited by 93 publications

References 46 publications

Diastereodifferentiating [2+2] photocycloaddition of chiral cyclohexenone carboxylates with cyclopentene by a microreactor

Diastereodifferentiating [2+2] photocycloaddition of chiral cyclohexenone carboxylates with cyclopentene by a microreactor

Photo-Claisen Rearrangement of Allyl Phenyl Ether in Microflow: Influence of Phenyl Core Substituents and Vision on Orthogonality

Green Photochemical Processes and Technologies for Research & Development, Scale‐up and Chemical Production

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