Oxazoles and Related Compounds

In the second method, oxazoles 150 have been prepared in good yields by HTIB-induced ring closure of enamine carboxylic acids 149 [91JCR(S)302]. 

Cycloaddition reactions involving thermal/photochemical/catalytic decomposition of iodonium ylides are applicable to oxazole derivatives 

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Several synthetic routes are available for oxazoles and related compounds. The first one, outlined in Scheme 41, is based on previously discussed syntheses of benzofurans (Scheme 17) and imidazoles (Scheme 40). Thus, a-aroyloxyacetophenones (147), which are obtained by HTIB-induced oxidation of 51 followed by treatment with para-substituted benzoic acids, can be cyclized to oxazoles 148 (95JIC129) (Scheme 41). 

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