Substituent effects in the ring-chain tautomerism of 4-alkyl-2-aryl substituted oxazolidines and tetrahydro-1,3-oxazines

The condensation products of 2‐aminoethanol or 3‐aminopropanol (bearing an alkyl substituent on the carbon adjacent to the nitrogen) with substituted benzaldehydes proved to exist in CDCl3 at 300 K as threecomponent tautomeric mixtures of the diastereomeric five‐ or six‐membered 1,3‐O,N‐heterocyclic...

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Bibliographic Details
Published in:Journal of heterocyclic chemistry 2007-11, Vol.44 (6), p.1465-1473
Main Authors: Juhász, Márta, Lázár, László, Fülöp, Ferenc
Format: Article
Language:English
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Summary:The condensation products of 2‐aminoethanol or 3‐aminopropanol (bearing an alkyl substituent on the carbon adjacent to the nitrogen) with substituted benzaldehydes proved to exist in CDCl3 at 300 K as threecomponent tautomeric mixtures of the diastereomeric five‐ or six‐membered 1,3‐O,N‐heterocyclic ring forms and the corresponding imines. For each equilibrium, the electronic effects of the 2‐aryl substituents were characterized by the Hammett equation. The steric effects of the alkyl groups could be described by Hansch‐type equations for the equilibria involving oxazolidine ring forms. While the alkyl substituents did not cause any significant effect on the ring cis‐chain and the ring trans‐chain equilibria for tetrahydro‐1,3‐oxazines, increasing bulk of the 4‐alkyl group increased the stability of the cyclic tautomers for the analogous oxazolidines.
ISSN:0022-152X
1943-5193
DOI:10.1002/jhet.5570440635