Premium
Substituent effects in the ring‐chain tautomerism of 4‐alkyl‐2‐aryl substituted oxazolidines and tetrahydro‐1,3‐oxazines
Author(s) -
Juhász Márta,
Lázár László,
Fülöp Ferenc
Publication year - 2007
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.5570440635
Subject(s) - chemistry , tautomer , substituent , alkyl , steric effects , ring (chemistry) , aryl , electronic effect , diastereomer , medicinal chemistry , oxazines , stereochemistry , organic chemistry
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 CDCl 3 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.