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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.
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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: