Amidative Cyclization of Alkynyl Esters to Access Pyrazin-1(2 H )-ones: Application to the Synthesis of Peramine and Dibromophakellin.

Herein, we report an efficient 1,5,7-Triazabicyclo[4.4.0]dec-5-ene (TBD)-catalyzed tandem intermolecular amidation and regioselective intramolecular 6- exo -dig cyclization of alkynyl esters to efficiently access pyrazine-1(2 H )-one scaffolds. This organo-catalyzed [5 + 1] annulation features a broad substrate scope concerning both annulating partners. Total syntheses of peramine and formal syntheses of dibromophakellin natural products were achieved to show the application potential of the method.