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New NO‐Donors with Antithrombotic and Vasodilating Activities, VII: Z/E ‐Isomerism in Thiazole‐ and 1,3,4‐Thiadiazole‐2‐nitrosimines
Author(s) -
Rehse Klaus,
Lüdtke Eberhard
Publication year - 1994
Publication title -
archiv der pharmazie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.468
H-Index - 61
eISSN - 1521-4184
pISSN - 0365-6233
DOI - 10.1002/ardp.19943271009
Subject(s) - chemistry , thiazole , substituent , stereochemistry , enthalpy , polar effect , moiety , medicinal chemistry , physics , quantum mechanics
In thiazole‐ (23 compounds) and 1,3,4‐thiadiazole‐2‐nitrosimines (20 compounds) Z/E ‐isomers were described by 1 H‐NMR‐spectroscopy. There is a mutual conversion of the isomers. The coalescence temp. (Tc) mostly is 310 K. In the thiazole series, however, for five compounds higher energy barriers are observed. This is due to substituents in 4‐position with electron withdrawing properties. The Tc is increased when the compounds are dissolved in water instead of DMSO. Hereby it is concluded that the isomers have Ze or Ee configuration. It is made probable that the low field signal for the substituent in 3‐position corresponds to the Ze ‐isomer, which has a slight preference. The free enthalpy of rotation, calculated approximately, is between 56.0 ( 1m ) and 73.7 kJ/mol ( 1r ).