During his fight against Minato, it seemed that Tobi was trying to send Minato to Kamui's dimension. Even if Tobi had succeeded, couldn't Minato just teleport to one of his special kunai using the Flying Thunder God technique? Tobi knew of the Flying Thunder God technique, so what did he want to accomplish by sending Minato to Kamui's dimension?
From this page about Kamui's abilities:
Despite not always being present, Obito could keep targets under genjutsu while they were confined inside this technique's pocket dimension, thus keeping them incapacitated for extended durations.
Tobi knew that he cannot defeat the Fourth Hokage so easily while keeping Kyuubi under his control, since controlling Kyuubi itself consumes a lot of chakra. Hence, he may have tried sending Minato to Kamui's dimension to keep him out of the equation.
Minato can teleport to his Flying Thunder God formulas (specially marked kunai), but it isn't revealed whether he can do it from a different dimension.
Just to add to the already given answer. From the wiki page of Space Time Ninjutsu
It appears that each specific space-time technique has its own unique dimensional void that other techniques cannot normally access. However, a user can synchronise their respective dimension with the other one to gain access to it. To achieve this feat, however, requires an enormous amount of chakra.