You can't ready an action to cast Sleep. It's not a legal ready action. It takes a full round to cast a Sleep spell.
{table]|A_|B_|C_|D_|E_
1|||||
2|||||
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4|||1||
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6|||||[/table]
There is a door at A-6 west, another at A-1 North, and another at E-3.
Where in the room are you?
And initiative lasts until I end it. That's a DM decision. ^.^