Everaldo Canuto

Using this plugin you can heve different URL’s for your WordPress frontend and 
backend.
<h4>Credits</h4>
This plugin is created by <a href="https://twitter.com/ecanuto" title="Everaldo Canuto" rel="friend nofollow ugc">Everaldo Canuto</a> with sponsorship from <a href="http://nuveo.com.br/" title="Nuveo" rel="friend nofollow ugc">Nuveo</a>.

WP Domains

Just works

Use different domains for backend (admin) and frontend on Wordpress.

Rebrandly

By installing this plugin and configuring it to connect with your Rebrandly account, 
you will be able to create branded links using the same domain as of your WordPress website/app.
Unlock the opportunity for your team to freely create branded links via Rebrandly, 
while still safely serving your own content from your WordPress application.
Here are a few steps necessary to use this:
<ol>
<li>Install the plugin in your WordPress</li>
<li>Connect the domain to Rebrandly as Alias Domain, and take note of the autogenerated value for the alias</li>
<li>Set the alias name in the Admin menu (Settings > Rebrandly) and Save your settings</li>
</ol>

Rebrandly Redirect

Connect your WordPress application with Rebrandly and create branded links re-using the same domain name

WP Domains vs Rebrandly Redirect