Katalýza reakcí přenosu vodíku typu Meerwein-Ponndorf-Verley pomocí zeolit-aminových komplexů

Veselá, Klára

Meerwein-Ponndorf-Verley (MPV) reduction is a selective hydrogen transfer reaction that converts carbonyl compounds to the corresponding alcohols under mild conditions, offering a safer alternative to conventional hydrogenation by avoiding the use of molecular hydrogen. Recently, Lewis acid zeolites, particularly Zr- and Sn-substituted beta zeolites, have been identified as effective catalysts. Although MPV reduction is typically highly selective, its selectivity can decrease when the substrate structure allows competing Lewis catalysed reactions. In such cases, the addition of organic bases can increase selectivity by forming zeolite-amine complexes, although the mechanism as well as the base structure-activity correlations are unknown. This study focuses on the MPV reduction of citronellal, a bio-derived aldehyde, in the presence of Zr- and Sn-beta catalysts, which suffers from side reactions like carbonyl-ene cyclization and acetalization. Small nitrogen-containing organic bases such as pyridine and N- methylpiperidine were used to increase the citronellol selectivity and to disclose the structure- activity correlations between the base and the selectivity improvement. A series of pyridine- derived bases shifted selectivity in favour of citronellol except 2,6-ditert-butylpyridine, which is...

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