Rotate one gameobject in 90 degree increments based on another gameobjects rotation.

What I'm trying to do is rotate Gameobject 1's Y axis based on the Y axis range of Gameobject 2.

So, for instance, if Gameobject 1 is angled anywhere between NorthWest and NorthEast, then Gameobject 2 should be facing exactly North, then if Gameobject 1 changes it's angle to anywhere between NorthEast and SouthEast, then Gameobject 2 should change it's angle to be exactly East.

I tried to do it based on the y angle of the objects but I think i was running into some kind of gimbal lock issue.