Regiochemical and Stereochemical Studies of the Intramolecular Dipolar Cycloaddition of Nitrones Derived from Quaternary Aldehydes

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Alkayar, Z.T.I. ; Adams, H. ; Coldham, I. (2016)
  • Publisher: Thieme Publishing

Three aldehydes each with a quaternary α-carbon stereocentre bearing an alkenyl, a phenyl, and a methyl ester group were treated with N-methylhydroxylamine. In each case bicyclic isoxazolidine products were formed by condensation to give intermediate nitrones that undergo intramolecular dipolar cycloaddition. The stereoselectivity was influenced by the α-carbonyl substituent, possibly by a hydrogen bond between CO and a nearby CH of the nitrone in the transition state (supported by DFT and X-ray studies), and the regioselectivity was affected by the length of the tether and by the presence of an ester on the alkene dipolarophile.
  • References (1)

    Jones, R. C. F.; Martin, J. N. in Synthetic Applications of 1,3-Dipolar Cycloaddition Chemistry Toward Heterocycles and Natural Products; Padwa, A., Pearson, W. H., Eds.; Wiley: New York, 2002, Chapter 1.

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