Applications of Activated Methylene Isocyanides in the Synthesis of Azoles

Synthesis of thiazoles by the base induced cyclization of active methylene isocyanides with dithioesters, xanthate esters, -oxodithioesters and 2-oxo-2-(amino) ethanedithioates are presented in this chapter. Besides, a tandem approach for the synthesis of oxazoles is developed by the oxidation of alcohols and arylmethyl bromides followed by cyclization with activated methylene isocyanides is also illustrated. In the same way, synthesis of oxazoles by the reaction of tosyl chloride with carboxylic acids followed by cyclization with tosylmethyl isocyanide (TosMIC) in the presence of a base is described. Finally, synthesis of imidazoles by the cyclization of TosMIC and ethyl isocyanoacetate with N(N), N'-di(tri)substituted carbamimidothioates is also presented. The probable mechanisms for the formation of azoles (thiazoles, oxazoles and imidazoles) are also given in this chapter.