The Heck synthesis of β‐arylated ketones catalyzed by palladium immobilized on functional polysiloxane microspheres

• Published in: Applied organometallic chemistry 2020-12, Vol.34 (12), p.n/a
• Main Authors: Wirwis, A., Mizerska, U., Cypryk, M., Trzeciak, A.M.
• Format: Article
• Language: English
• Subjects: Catalysts; Chemical synthesis; Chemistry; Functional groups; Heck coupling; Isomerization; Ketones; Microspheres; Palladium; polysiloxane microspheres; tandem reaction; β‐arylated ketones
• ISSN: 0268-2605; 1099-0739
• DOI: 10.1002/aoc.5969

Palladium catalysts, obtained by the impregnation of Pd(OAc)2 on aminopropyl‐ or pyridine‐functionalized polysiloxane microspheres, were used in the Heck reaction of iodobenzene with 3‐buten‐2‐one and 3‐buten‐2‐ol at 120°C using an oil bath or microwave heating. The synthesis of 4‐phenyl‐3‐buten‐2‐one was one‐step arylation of ketone while 4‐phenyl‐2‐butanone was formed in two‐step arylation–isomerization sequential transformation of alcohol. A very low palladium loading, 0.05 mol%, was sufficient to obtain a yield of ketones higher than 90%. In recycling experiments, an effect of the functional group present in polysiloxane was observed and much better results were obtained for the aminopropyl‐modified polymer. The catalyst was easily retrieved and reused in eight consecutive runs in the reaction of 3‐buten‐2‐one, while with 3‐buten‐2‐ol 11 subsequent cycles were performed with practically the same yield. Palladium catalysts, immobilized on functionalized polysiloxane microspheres, catalyzed the Heck coupling of iodobenzene with 3‐buten‐2‐ol and 3‐buten‐2‐one. Both substrates were selectively transformed to the expected aryl ketones at a low palladium loading of 0.05 mol%. In recycling experiments, an effect of the functional group of polysiloxane was observed, better results being obtained with the aminopropyl than with the pyridine function.