It is quite usual to see a leopard in a tree. After all, these big cats climb up there quite commonly and often bring their dead prey into the high branches to protect them from the competition (like a wandering hyena). But it is quite rare to see a leopard hunt in a treee. When, it is confronting an eagle, we reach great heights of weirdness.
Anyway, Paul Steyn observed such a behaviour (a leopard female trying to enter the nest of an eagle). But, in the end, even if the eagle flew avoding any risk, the leopard did not catch anything.