Abstract
An operationally facile and efficient protocol has been developed for the construction of various 1,3‐oxazole‐containing heterocycles with excellent yields of up to 94 %. This protocol proceeds through a diphenylphosphoryl azide (DPPA)‐mediated reaction cascade on substituted 2‐aminonicotinic acids/2‐aminoanthranilic acids with ethyl isocyanoacetate/p‐toluenesulfonylmethyl isocyanides by forming C−C, C−O, and C−N bonds in a single operation. The synthetic utility of this transformation is also extended through a scaled‐up synthesis and C−H activation. The salient features such as metal‐free, mild reaction conditions, higher yields, and clean reactions make the protocol a useful contribution to the synthesis of medicinally useful heterocycles.
1,3‐Oxazole‐containing heterocycles: An effective and fascinating method has been developed for the construction of various fused oxazole‐containing quinolinones, naphthyridinones, and tosyloxazol‐5‐yl pyridines by a diphenylphosphoryl azide‐mediated reaction cascade on substituted 2‐aminonicotinic acids/2‐aminoanthranilic acids with ethyl isocyanoacetate/p‐toluenesulfonylmethyl isocyanides.