Piperazine, 1-(3-butynyl)-4-methyl- (9CI)

1-But-3-ynyl-4-methylpiperazine is used as a reactant in the preparation of alkynoylamino (arylamino)quinazolines or (arylamino)pyridopyrimidines and their activities as irreversible inhibitors of erbB tyrosine kinases such as erbB1, erbB2, and erbB4.