Y. Nagao, Hitoshi Iimori, S. Goto
Feb 25, 2002
Citations
0
Influential Citations
17
Citations
Journal
Tetrahedron Letters
Abstract
X-Ray crystallographic structures of 5-ethyl-2-trifluorothioacetylamino-1,3,4-thiadiazole 2 , 5-ethyl-3- p -nitrobenzyl-2-trifluorothioacetylimino-1,3,4-thiadiazoline 4 and 5- n -propyl-2-trifluoroacetylamino-1,3,4-thiadiazole 7 proved to be monomeric or dimeric bearing intermolecular hydrogen bondings and/or an intramolecular nonbonded 1,5-type S⋯S or S⋯O interactions. In contrast, the X-ray crystallographic structure of 5-ethyl-2-trifluoroacetylamino-1,3,4-oxadiazole 5 was shown to be dimeric involving ordinal intra- and intermolecular hydrogen bondings without any close contact. The ab initio computational studies (HF/6-311G*) of the four monomeric formylamino- and thioformylaminothiadiazoles(or -oxadiazoles) and formylimino- and thioformyliminothiadiazolines(or -oxadiazolines) structures 8 – 11 clarified the relative structure–stability order and a remarkable discrepancy in the predominant structures of the acylamino- and thioacylaminothiadiazoles and -oxadiazoles having the potential for rotational, geometrical and tautomeric isomerism.