To find id whose value is equal to the id of an array of ids:
$this->YourModel->find(\'all\', array( \'conditions\' => array( \"YourModel.id
This should work:
$this->YourModel->find('all', array( 'conditions' => array( "NOT" => array( "YourModel.id" => array(1, 2, 3, 4) ) ) ));
http://book.cakephp.org/2.0/en/models/retrieving-your-data.html#complex-find-conditions