Ethyl 2-chlorooxazole-4-carboxylate: a versatile intermediate for the synthesis of substituted oxazoles.

[reaction: see text] By using a sequence of regiocontrolled halogenation and palladium-catalyzed coupling reactions, the synthesis of variously substituted oxazoles from ethyl 2-chlorooxazole-4-carboxylate (2) was accomplished. The methodology was applied to the synthesis of a series of 2,4-disubstituted, 2,5-disubstituted, and 2,4,5-trisubstituted oxazoles.