Photocycloaddition of 5-Methoxyoxazoles to Aldehydes and α-Keto Esters: A Comprehensive View on Stereoselectivity, Triplet Biradical Conformations, and Synthetic Applications of Paternò–Büchi Adducts
Axel G. Griesbeck A B and Samir Bondock AA Department of Chemistry, University of Cologne, Greinstr. 4, 50939 Köln, Germany.
B Corresponding author. Email: griesbeck@uni-koeln.de
Australian Journal of Chemistry 61(8) 573-580 https://doi.org/10.1071/CH08168
Submitted: 21 April 2008 Accepted: 28 May 2008 Published: 15 August 2008
Abstract
The photocycloaddition of carbonyl compounds (aldehydes and keto esters, respectively) with 5-methoxyoxazoles bearing substituents at C2 and C4 is described with respect to regio- and diastereoselectivity. In all cases the reactions proceed with excellent regioselectivity and with high to moderate (exo) diastereoselectivity independent of the nature of the excited carbonyl compound. The products can be easily ring-opened to give α-amino, β-hydroxy carboxylic acid derivatives.
Acknowledgements
This work was supported by the Deutsche Forschungsgemeinschaft (DFG), the Fonds der Chemischen Industrie, and the Eqyptian Government (Ph.D. grant for S.B.).
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