Synthesis of pyrazolo[1,5-c]quinazoline derivatives through the copper-catalyzed domino reaction ofo-alkenyl aromatic isocyanides with diazo compounds

A novel copper-catalyzed domino reaction betweeno-alkenyl aromatic isocyanides and diazo compounds has been developed under mild reaction conditions. Variouso-alkenyl aromatic isocyanides were prepared from readily available reactants. The reaction provides a general and efficient method for the synthesis of pyrazolo[1,5-c]quinazolines by the formation of two rings and three new bonds in a single step from readily available acyclic starting materials. A mechanism involving a tandem (3+2) cyclization/elimination/intramolecular aza-addition sequence was proposed.