<span class="dropdown">
  <a class="btn btn-mini btn-info dropdown-toggle insert-gallery" id="dLabel" role="button" data-media-id="50" data-toggle="dropdown" href="#">
    Add To Gallery
    <b class="caret"></b>
  </a>
  <ul class="dropdown-menu" role="menu" aria-labelledby="dLabel"></ul>
</span>

$('.insert-gallery').on('click', function(){
  var media_id = $(this).data('media-id');
  console.log(media_id);
  console.log('click');
});

$(document).on("click", ".dropdown-toggle", function(event) {
  // Ajax actions here
  $(this).attr("data-toggle", "dropdown").click();
});