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A Study in the Mechanism of the Formation of Substituted Uracils and Thiouracils
Author(s) -
Ma T.S.,
Zoellner William G.
Publication year - 1957
Publication title -
journal of the chinese chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.329
H-Index - 45
eISSN - 2192-6549
pISSN - 0009-4536
DOI - 10.1002/jccs.195700007
Subject(s) - thiourea , chemistry , ethyl acetoacetate , alkyl , acetoacetic ester synthesis , yield (engineering) , urea , organic chemistry , molecule , medicinal chemistry , catalysis , materials science , metallurgy
A variety of ureas and thioureas were treated with ethyl acetoacetate, ethyl n‐butylacetoacetate, and ethyl di‐n‐butylacetoacetate under acidic, basic, and neutral conditions. Under acidic conditions, ethyl acetoacetate reacted only with urea or methylurea; under neutral conditions, it reacted only with thiourea; under basic conditions, it reacted only with thiourea, methylthiourea and ethylthiourea. Ethyl n‐butylacetoacetate reacted only with thiourea in base, while ethyl di‐n‐butylacetoacetate failed to condense with urea or thiourea under all conditions. In the condensation reaction between acetoacetic ester and thioureas, it was found that (a) the reaction proceeded best with thiourea and ethyl acetoacetate; (b) introduction of a single alkyl group into either the thiourea or the acetoacetic ester molecular lowered the yield but did not preclude the reaction; (c) introduction of two alkyl groups distributed in any fashion between the thiourea and acetoacetic ester molecules precluded the reaction; and (d) only the 3‐alkyl thiouracils were obtained from alkyl thioureas. A probable mechanism, based on the resonance theory, has been proposed.