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Non‐Dipolar Behavior of Mesoionic Heterocycles: Synthesis and Tautomerism of 2‐Alkylthioisomünchnones
Author(s) -
Ávalos Martín,
Babiano Reyes,
Cintas Pedro,
Díaz Jesús,
Jiménez José L.,
López Ignacio,
Palacios Juan C.
Publication year - 2004
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.200400049
Subject(s) - mesoionic , chemistry , tautomer , atropisomer , aryl , halide , alkyl , alkylation , computational chemistry , medicinal chemistry , stereochemistry , organic chemistry , catalysis
This paper describes a general preparation of a series of 1,3‐thiazolium‐4‐olates, each bearing an alkyl group at C‐2, through reactions between N ‐arylthiocarboxamides and α‐haloacyl halides. Unlike the 2‐aryl‐substituted derivatives, such alkylated mesoionic compounds exist in equilibria with their non‐dipolar tautomers, the corresponding 2‐alkylidene‐1,3‐thiazolidin‐4‐ones. The unambiguous characterization of such tautomers and their relative stabilities have now been assessed by spectroscopic and computational studies. The presence of o , o′ ‐disubstituted aryl groups at N‐3 of the heterocyclic ring slows down free rotation around the N−Ar bond, thus opening access to a promising class of non‐biaryl atropisomers. Finally, treatment of N ‐arylthioformamides with α‐haloacyl halides gives rise to N ‐acylthioformamides instead of the corresponding mesoionic species. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)