Synthesis of Indole‐Fused Pyrazino[1,2‐a]quinazolinones by Copper(I)‐Catalyzed Selective Hydroamination‐Cyclization of Alkynyl‐tethered Quinazolinones

We described a copper(I)‐catalyzed atom economic and selective hydroamination‐cyclization of alkynyl‐tethered quinazolinones to prepare a variety of indole‐fused pyrazino[1,2‐a]quinazolinones in good to excellent yields ranging from 39 %–99 % under mild reaction conditions. Control experiments revealed that coordination‐directed method of quinazolinone moiety with copper(I) was important for the selective hydroamination‐cyclization of alkynes at the N1‐atom instead of N3‐atom of quinazolinone. The reaction could be easily performed at gram scales and some prepared indole‐fused pyrazino[1,2‐a]quinazolinones with donating groups on the indole moiety showed a distinct fluorescence emission wavelength with blue shift under the acid conditions. We described a copper(I)‐catalyzed atom‐economic and highly chemo‐selective hydroamination‐cyclization of alkynyl‐tethered quinazolinones to prepare a variety of indole‐fused pyrazino[1,2‐a]quinazolinones in good to excellent yields under mild reaction conditions.