110960-40-2Relevant academic research and scientific papers
The Hantzsch Thiazole Synthesis under Acidic Conditions: Change of Regioselectivity
Bramley, (Miss) Susan E.,Dupplin, Viscount,Goberdhan, Dhanesh G. C.,Meakins, G. Denis
, p. 639 - 644 (2007/10/02)
The condensation of α-halogeno ketones with N-monosubstituted thioureas in neutral solvent leads exclusively to 2-(N-substituted amino)thiazoles.In the present work it was shown that under acidic conditions mixtures of 2-(N-substituted amino)thiazoles and 3-substituted 2-imino-2,3-dihydrothiazoles are formed. (The isomers were distinguished by characteristic differences between their 5-H 1H n.m.r. signals and the i.r.CO bands of their trifluoroacetate derivatives.) The proportions of the 2-imino-2,3-dihydrothiazoles in the mixtures are influenced by experimental features and by the structures of the starting materials.Reactions in 10 M-HCl-EtOH (1:2) at 80 deg C for 20 min were found to be the most efficient for generating 2-imino-2,3-dihydrothiazoles; in the most favourable case 2-imino-3,4-dimethyl-2,3-dihydrothiazole was obtained in 73 percent yield.A possible explanation of the results is discussed.
