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Visible Light‐Promoted Beckmann Rearrangements: Separating Sequential Photochemical and Thermal Phenomena in a Continuous Flow Reactor
- Source :
- European Journal of Organic Chemistry
- Publication Year :
- 2019
- Publisher :
- John Wiley and Sons Inc., 2019.
-
Abstract
- The Beckmann rearrangement of oximes to amides typically requires strong acids or highly reactive, hazardous electrophiles and/or elevated temperatures to proceed. A very attractive alternative is the in situ generation of Vilsmeier-Haack reagents, by means of photoredox catalysis, as promoters for the thermal Beckmann rearrangement. Investigation of the reaction parameters for this light-induced method using a one-pot strategy has shown that the reaction is limited by the different temperatures required for each of the two sequential steps. Using a continuous flow reactor, the photochemical and thermal processes have been separated by integrating a flow photoreactor unit at low temperature for the electrophile generation with a second reactor unit, at high temperature, where the rearrangement takes place. This strategy has enabled excellent conversions and yields for a diverse set of oximes, minimizing the formation of side products obtained with the original one-pot method.
Details
- Language :
- English
- ISSN :
- 1434193X
- Volume :
- 2019
- Issue :
- 11
- Database :
- OpenAIRE
- Journal :
- European Journal of Organic Chemistry
- Accession number :
- edsair.pmid..........22bfc6a9c5e1b6209b11e44d6bada123