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Issue 48, 2019
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Electronic effects in tautomeric equilibria: the case of chiral imines from d-glucamine and 2-hydroxyacetophenones

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Abstract

A one-pot procedure for preparing a series of chiral imines by direct condensation of D-glucamine with 2-hydroxyacetophenones is described. Under conventional acetylation an unexpected mixture of two different peracetylated molecules is obtained, one with an open enamine structure, and the other incorporating an N-acetyl-1,3-oxazolidine into the acyclic skeleton. Surprisingly, both molecules coexist within the crystal's unit cell, as inferred from single-crystal X-ray analysis of a 5-bromo-substituted aryl derivative. Moreover, the 1,3-oxazolidine ring exists as rotational conformers (E,Z) owing to the restricted rotation around the N-acetyl bond. The equilibrium involving imine and enamine structures has been assessed in detail, providing in addition linear free-energy relationships between the tautomerization constants (KT) and the electronic effect of the substituents.

Graphical abstract: Electronic effects in tautomeric equilibria: the case of chiral imines from d-glucamine and 2-hydroxyacetophenones

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Publication details

The article was received on 04 Oct 2019, accepted on 15 Nov 2019 and first published on 19 Nov 2019


Article type: Paper
DOI: 10.1039/C9OB02147G
Org. Biomol. Chem., 2019,17, 10209-10222

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    Electronic effects in tautomeric equilibria: the case of chiral imines from D-glucamine and 2-hydroxyacetophenones

    E. Matamoros, P. Cintas, M. E. Light and J. C. Palacios, Org. Biomol. Chem., 2019, 17, 10209
    DOI: 10.1039/C9OB02147G

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