<div class="btn-group">
 <button type="button" class="btn btn-md btn-success">Inserer lien site mobile</button>
 <button type="button" class="btn btn-md btn-success dropdown-toggle" data-toggle="dropdown">
 <span class="caret"></span>
 <span class="sr-only">Toggle Dropdown</span>
</button>
<ul class="dropdown-menu" role="menu">
    <li><a href="#">Menu accordéon version site1</a></li>
    <li><a href="#">Menu accordéon version site2</a></li>
    <li><a href="#">Menu accordéon version site3</a></li>
</ul>
</div>