Setting up redirects from routes.php
I'd try and avoid the routes.php route (pun intended).  There isn't any need to get Craft involved in a redirect when your web server (Apache?) can handle it much faster.

If you're using Apache, then adding something like this to your public .htaccess file should do the trick:

RewriteRule ^fiveminutes$ /5minutes [NC,R=301,L]


Update:

Missed the part where you said this was in a plugin.  In that case you'd want to setup something like this in your main plugin's class file:

public function registerCpRoutes()
{
    return array(
        'fiveminutes' =&gt; array('action' =&gt; 'myPluginController/fiveMinuteRedirect'),
   );
}


Then from your MyPluginController.php class have an actionFiveMinuteRedirect() method that simply did a permanent redirect:

`$this-&gt;redirect('5minutes', true, 301);`