Rhodium(III)‐Catalyzed Formal Cycloaddition between Thienopyridine/Thienopyrazine Carboxylic Acids and Alkynes, Triggered by C−H Activation

Abstract In the last decade, a number of metal‐catalyzed technologies for functionalization C−H bonds in carbonaceous aromatic substrates have been developed. However, similar reactions with aza‐heteroaromatic precursors are more challenging and much less Herein, we report first time catalytic formal cycloadditions N,S ‐heterocycles featuring carboxylic acid substituents, unsaturated partners (alkynes). The reaction, which works different symmetrical unsymmetrical alkynes, produces appealing tricyclic ɑ‐pyrones straightforward manner. optimized conditions established model reaction employing thieno[2,3‐ b ]pyridine‐2‐carboxylic as substrate, involved use Ag 2 CO 3 /AgSbF 6 additives, proved to be general alkynes. Moreover, analogous using thieno[3,2‐ ]pyrazine‐6‐carboxylic were successfully Overall, this technology allows build, single step, an interesting variety pharmaceutically relevant exhibiting nitrogen sulfur heteroatoms.