Change a div content after click on another div
You need to conform to the coding standards and make it anonymous so it doesnt conflict with jQuery.

(function ($) {
  Drupal.behaviors.mybehavior = {
    attach: function (context, settings) {
      var selector = '.title-noticia a';

      $(selector).click(function(e) {
        e.preventDefault();
      }

      $.ajax({
        url: $(this).attr('href') + '?ajaxrequest',
        success: function(data) {
          $('.region-content').replaceWith(data);
        }
      });
    });
  });
})(jQuery);


See more: https://www.drupal.org/docs/7/api/javascript-api/managing-javascript-in-drupal-7

Your behavior will be called automatically, so there is no need for $(document).ready.