Create a redirect to a path using the redirect module.

Drupal: Create redirect

// Apply redirect from old content to new content.
$old_alias = 'some/old/path';
$new_alias = 'node/' . $node->nid;
$redirect = new stdClass();
redirect_object_prepare($redirect);
$redirect->source = $old_alias;
$redirect->redirect = $new_alias;

redirect_save($redirect);