125759-82-2Relevant articles and documents
Azoles. Part 8. Metallation and Bromine -> Lithium Exchange Reactions of Polyhalogenothiazoles
Athmani, Salah,Bruce, Andrew,Iddon, Brian
, p. 215 - 219 (2007/10/02)
2,4-Dichloro- and 2,4-dibromo-thiazole were deprotonated at position-5 with LiN(iPr)2 in THF at -78 deg C and the resulting lithium compound was quenched with various reagents, to yield various trisubstituted thiazoles. 2,5-Dibromo-4-chlorothiazole reacted with n-butyllithium in THF at -78 deg C at position-5 and the resulting lithium derivative gave 2-bromo-4-chloro-5-substituted thiazoles when quenched with the appropriate reagent.Both the 2- and 5-bromine-atoms were reactive in diethyl ether. 2,5-Dibromothiazole failed to deprotonate at position-4 under various reaction conditions, whereas treatment of 2,4,5-tribromothiazole with 1 mole equivalent of n-butyllithium in THF at -90 deg C, followed by addition of dimethyl disulfide after 30 min, gave a high yield of the 2,5-bis(methylthio)-compound.The tribromo-compound was also treated with 1 mole equivalent of n-butyllithium or methyllithium under various reaction conditions and the products formed after hydrolysis were analysed by 1H NMR spectroscopy.The 5-bromine-atom is the most reactive and greater selectivity is obtained with methyllithium.
