Neue optisch aktive Phosphoniumsalze als Phasentransferkatalysatoren sowie die Verwendung der korrespondierenden Phosphane in der asymmetrischen Katalyse

Within this thesis, primary the application of optically active phosphoniumsalts in asymmetric phase transfer catalysis is described. Emphasis is placed on the Darzens-reaction of benzaldehyde and chloroacetophenone. First, achiral phosphoniumsalts were used under variation of the structure of the salt, temperature, reaction time and base. This was followed by the synthesis of polymerbound alkltriphenylphosphonium iodides , which were repeatedly used up to 18 times in a row as phase transfer catalysts. To obtain optically active phosphoniumsalts, first optically active phosphane precursors were quarternised with methyl iodine. Subsequently, phosphoniumsalts were derived from diphenylphosphino benzoic acid amides. The use of diphenylphosphino benzoic acid pentafluorophenol esters paved the way for the synthesis of a wide range of amides, which were obtained by conversion with diverse amines. It was found that sterically demanding substituents in alpha-position to the amide group led to the highest enantiomeric excesses, whereas the enantioselectivity dropped in case of substitution at the beta position. The highest enantiomeric excess was obtained with the methyl phosphonium iodine of ortho-diphenylphosphino benzoic acid coupled with adamantyl glycinole in 36% ee and 13% yield. The role of the hydroxy group is not clear yet, however it appears that an sp3-Carbon in alpha-position to the nitrogen of the amide group has an advantage. The application of an "inverse" salt derived from diphenylphosphino aniline, as well as optically active oxosulfoniumsalts and optically active copper complexes, led to racemic products. Quite interesting results were observed with an optically active P-chiral phosphoniumsalts, although products were generated with moderate enantioselectivities and yields (7%ee and 8% yield). Except two, the corresponding phosphanes are not reported in literature to date. Thus, they were tested as ligands in numerous metal-catalyzed reactions including: rhodium catalyzed hydrosilylation, palladium catalyzed allylic substitutions, hydroamination of cyclohexadiene, hydrovinylation, rhodium-catalyzed 1,2-addition and ruthenium catalyzed transfer hydrogenation.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2003

Author dc:creator

• Köhler, Manuela

Contributors dc:contributor

• Bolm, Carsten

• info:eu-repo/classification/ddc/540
• Darzens-Reaktion
• Asymmetrische Reaktion
• Phasentransfer-Katalyse
• Phosphoniumsalze
• Optisch aktive Verbindungen
• Chemie
• asymmetrische Phasentransferkatalyse
• Phosphane

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

ger

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-123520%22

OAI identifier oai:identifier

oai:publications.rwth-aachen.de:61907