Using a 2,3-diamino pyrazine substrate and yttrium triflate catalyst, various 2-alkyl and aryl substituted 3,8-diaminoimidazo[1,2-a]pyrazines were efficiently prepared through Groebke–Blackburn–Bienaymé MCR. In particular, a novel 2-piperonyl 3,8-diaminoimidazo[1,2-a]pyrazine structure was prepared exclusively with this new method and was found to have moderate Hsp90 inhibitory activity. A crystalline complex with N-terminus ATP domain of Hsp90 and one of the new Hsp90 inhibitors was also obtained to elucidate the origin of activity of 2-piperonyl 3,8-diaminoimidazo[1,2-a]pyrazines.