Endo-benzonorbornen-2-ol as an efficient non-natural chiral auxiliary in the asymmetric aza-Diels–Alder reactions between cyclopentadiene and (1-phenylethyl)iminoacetates

Exo-2-azabicyclo[2.2.1]hept-5-enes were obtained by cycloaddition reactions between cyclopentadiene and protonated (S)- and (R)-1-phenylethylimines of (1R,endo)-benzonorbornen-2-yl glyoxylate. The non-natural (1R,endo)-benzonorbornen-2-ol proved to be an efficient chiral auxiliary in these asymmetri...

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Published inRSC advances Vol. 4; no. 101; pp. 57768 - 57772
Main Authors Sousa, Carlos A. D., Maestro, Miguel A., Garcia-Mera, Xerardo, Rodríguez-Borges, José E.
Format Journal Article
LanguageEnglish
Published 01.01.2014
Subjects
Adducts
Asymmetry
Chromatography
Cycloaddition
Cyclopentadiene
Optical properties
Optical rotation
X-rays
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Summary:Exo-2-azabicyclo[2.2.1]hept-5-enes were obtained by cycloaddition reactions between cyclopentadiene and protonated (S)- and (R)-1-phenylethylimines of (1R,endo)-benzonorbornen-2-yl glyoxylate. The non-natural (1R,endo)-benzonorbornen-2-ol proved to be an efficient chiral auxiliary in these asymmetric aza-Diels-Alder reactions, which afforded only exo-cycloadducts with 1S : 1Rdiastereomer ic ratios of 15 : 85 for (S)-(1-phenylethyl)imine and 93 : 7 for (R)-(1-phenylethyl)imine. The obtained diastereoisomers were effortlessly and efficiently isolated using a chromatographic column. The absolute configuration of all the formed adducts was unequivocally assigned through NMR, specific optical rotation and X-ray data.
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ISSN:2046-2069
2046-2069
DOI:10.1039/C4RA11143E