Suggest the syntheses of putrescine and cadaverine from ethyl bromide

I don't think I can use Grignard can I? PLEASE HELP.

CH3CH2Br + CH3CH2Mg/EtoEt -> CH3Ch2Ch2Ch2MgBr + NaN3/EtOH -> CH3Ch2Ch2Ch2N=N=N + LiAlH4/H20 CH3Ch2Ch2Ch2NH2?

Then what? does this even work?