Synthesis of pyrimidine-fused skeletons through copper-catalyzed consecutive Sonogashira coupling and aminocyclization†
Abstract
A copper-catalyzed sequence involving a Sonogashira coupling reaction and 5-exo-dig aminocyclization between a terminal alkyne and a 2-(2-bromophenyl)pyrimidine analog based on six-membered rings is presented. This protocol provides a controlled and modular approach to access a variety of synthetically useful pyrimidine-fused skeletons with high efficiency, broad substrate scope, and excellent functional group compatibility. Under acidic conditions, the (Z)-configuration of products spontaneously converts into (E)-9-benzylidene-1,9-dihydro-11H-pyrazolo[4′,3′:4,5]pyrimido[2,1-a]isoindol-11-ones.