Bicyclische Triazoliumsalze als Präkatalysatoren in der asymmetrischen Benzoin- und Acyloinkondensation und asymmetrische Synthese von Oxazolidin-2-onen

In this work the synthesis of a novel enantiopure bicyclic triazolium salt and its application as an efficient chiral catalyst in the form of the corresponding Wanzlick carbene in the asymmetric variant of the benzoin condensation is described. The chiral bicyclic triazolium salt is currently the most efficient precatalyst for the asymmetric benzoin condensation. The substituted acyloins are obtained in moderate to good yields (8 - 83%) and with very good enantiomeric excesses (80 - 95%) from the corresponding aldehydes. The high asymmetric induction is presumably based on the conformational rigidity of the bicyclic nucleophilic carbene catalyst and on the steric hindrance in the Breslow intermediate. The asymmetric synthesis of cis-4,5-disubstituted oxazolidin-2-ones is described. Following a four step reaction sequence of alpha-alkylation, 1,2-addition with subsequent carbamate protection, cyclization and concluding with cleavage of the auxiliary the title compounds are obtained in moderate yields and in excellent diastereo- and enantiomeric excesses (de = 88 - >96%, ee = >96%). The oxazolidinone structure is often found in natural and synthetic pharmacologically active molecules like Zyvox (Linezolid) or Streptazolin. In addition, application of oxazolidinones in asymmetric synthesis are well known, especially the widely used auxiliaries of Evans et al.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2002

Author dc:creator

• Kallfaß, Ulrike Silvia Gottfriede

Contributors dc:contributor

• Enders, Dieter

• info:eu-repo/classification/ddc/540
• Chemie
• asymmetrische Synthese
• Carbene
• Triazoliumsalze
• Oxazolidinone
• Benzoinkondensation

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

ger

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-123765%22

OAI identifier oai:identifier

oai:publications.rwth-aachen.de:62176