One-pot synthesis of chloroalcohols and their lipase mediated kinetic resolution - ferrocenyl aziridinylmethanols as chiral ligands in enantioselective conjugate diethylzinc addition to enones

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2007

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İşleyen, Alper

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An unexpected tricyclic ether formation instead of acetate addition to the double bond of a norbornene derivative aroused our interest to explore the mechanism of this reaction. Mechanistic studies showed that methylene diacetate (MDA) was formed in the stock solution (NBu4OAc + dichloromethane) and decomposed to formaldehyde under Lewis or Brønsted acid conditions. Formaldehyde and olefin condensation (Prins reaction) clearly explains the formation of the unexpected product. Same methodology was then successfully applied to develop a one-step procedure for the synthesis of 3-chloro-3-arylpropanols, which are important starting materials for the synthesis of biologically active benzanilide derivatives. Styrenes were reacted with MDA in the presence of boron trifluoride to give the corresponding 3-chloro-3-arylpropanols in 3684% yield. The second part of the thesis involves kinetic resolution of 3-chloro-3-arylpropanols by lipase mediated acylation which are described for the first time. Acylation with the CCL provided the best enantioselectivity amongst the enzymes used. Enantiomerically enriched products with up to 78% ee were obtained after two successive lipase-mediated acylations. Different substituents on the aromatic ring and bromide, instead of chloride, at the benzylic position of the substrates were found to have no drastic influence on the enantioselectivity of the reaction. In the last part, easily available ferrocenyl substituted aziridinylmethanols (FAM) were complexed with nickel to catalyze the enantioselective diethylzinc addition to various enones with ee’s reaching 82%. The ligands can be recovered and used without losing their activity. The sense of asymmetric induction was found to be dependent on the configuration of the aziridine ring.

Subject Keywords

Chemistry, Organic

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http://etd.lib.metu.edu.tr/upload/12608857/index.pdf
https://hdl.handle.net/11511/17212

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Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats

A. İşleyen, “One-pot synthesis of chloroalcohols and their lipase mediated kinetic resolution - ferrocenyl aziridinylmethanols as chiral ligands in enantioselective conjugate diethylzinc addition to enones,” Ph.D. - Doctoral Program, Middle East Technical University, 2007.