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Aldol reactions of conformationally stable o-CF3 phenyl bearing axially chiral thiohydantoins

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dc.contributor Graduate Program in Chemistry.
dc.contributor.advisor Doğan, İlknur.
dc.contributor.author Bacak Erdik, Melis.
dc.date.accessioned 2023-03-16T11:01:02Z
dc.date.available 2023-03-16T11:01:02Z
dc.date.issued 2021.
dc.identifier.other CHEM 2021 B33
dc.identifier.uri http://digitalarchive.boun.edu.tr/handle/123456789/14410
dc.description.abstract Novel axially chiral thiohydantoin derivatives bearing an o-CF3 phenyl ring have been synthesized atroposelectively from the reaction of R and S alanine, phenyl alanine and valine methyl ester HCl salts with ortho-trifluoromethylphenyl isothiocyanate in the presence of triethyl amine (TEA). It was found that after purification of the crude product by simple recrystallization, starting with R amino acids, the products were obtained possessing only M axial chirality whereas starting with S amino acids, only the P isomers were obtained. When the size of the substituent at C5 increased, the RM/SM and the SP/RP ratios increased significantly. The nonaxially chiral thiohydantoins have been shown to have a racemic form. The axially chiral stereoisomers of the products have been identified by comparing their 1H NMR spectra with their HPLC chromatograms. The axially chiral isomers were found to be conformationally and configurationally stable at room temperature. Sterically controlled aldol reactions on M and P thiohydantoins with benzaldehyde and furaldehyde have been carried out and the isomeric products were identified. It was found that during the aldol reaction of alanine and valine derivatives, the o-trifluoromethyl group of the M isomers shielded the Si face of the intermediate enolate and in this way enabled the selective formation of only the R configured aldol products at C5 of the heterocyclic ring. The otrifluoromethyl group of the P thiohydantoins on the other hand shielded the Re face of intermediate enolate and caused the formation of only the S configured aldol products at C5. However, this steric control has not been observed during the aldolization of the phenyl alanine derivatives. A face selectivity of the benzaldehyde and furaldehyde molecules for compound 5 and compound 2 have been observed as 91:9 and 78:22 respectively.
dc.format.extent 30 cm.
dc.publisher Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2021.
dc.subject.lcsh Aldol condensation.
dc.subject.lcsh Chirality.
dc.title Aldol reactions of conformationally stable o-CF3 phenyl bearing axially chiral thiohydantoins
dc.format.pages xx, 150 leaves ;


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