From the Wikipedia entry:
The third and last season of Star Wars: Clone Wars gives the audience a look at Obi-Wan Kenobi and Anakin Skywalker's adventures in the Outer-Rim Terrortories as mentioned in Star Wars Episode III: Revenge of the Sith. Anakin is knighted into a Jedi Knight and Coruscant comes under attack by the Confederacy of Independent Systems, as a diversion for General Grevious to sneak in and capture Chancellor Palpatine.
It's easy to see why Lucasfilm would want to squelch interest in Tales of the New Republic. For one thing, with the animators of Clone Wars transforming it it into a 3D, CGI-style for the 3rd season, its look is similar to that of Tales of the New Republic. Here is the teaser trailer: