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Computational studies of the cyclization of thiosemicarbazides
Author(s) -
Siwek Agata,
Paneth Piotr
Publication year - 2007
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.1179
Subject(s) - chemistry , anhydrous , moiety , acetic acid , ring (chemistry) , imidazolidine , substituent , derivative (finance) , medicinal chemistry , molecule , thiadiazoles , computational chemistry , stereochemistry , organic chemistry , financial economics , economics
While typically cyclodehydration of thiosemicarbazides in acidic media leads to 1,3,4‐thiadiazoles, we have recently shown that under reflux conditions in anhydrous acetic acid the cyclization yields an imidazolidine derivative. The mechanism of this reaction has been characterized theoretically. Calculations indicate that this direction, facilitated by the presence of the CH 2 CO 2 moiety in the N4 substituent is favored over the direction leading toward the thiadiazole product. Formation of the CN bond that closes the five‐member ring appears to be concerted with the departure of ethanol molecule, although the proton transfer from the nitrogen atom to oxygen atom is much more advanced in the transition state. Copyright © 2007 John Wiley & Sons, Ltd.