A student intends to synthesise compound Z, (CH3CH(OH)CH2CH2CH2NH2\text{CH}_3\text{CH(OH)CH}_2\text{CH}_2\text{CH}_2\text{NH}_2CH3CH(OH)CH2CH2CH2NH2), from 4-bromobut-1-ene, (H2C=CHCH2CH2Br\text{H}_2\text{C}=\text{CH}\text{CH}_2\text{CH}_2\text{Br}H2C=CHCH2CH2Br), as shown in the flowchart below.

Plan this synthesis showing reagents, the structures of intermediate 1 and intermediate 2, and equations for each stage. Explain why Stage 2 must be carried out before Stage 3.