<?php
$args = array(
	'post_type' => 'posts',
	'posts_per_page' => 99,
	'orderby' => 'parent',
	'order' => 'ASC'
);
$posts = get_posts( $args );
foreach ( $posts as $post ) {
	$childargs = array(
		'post_type' => 'posts',
		'child_of' => $post->ID
	);
	$children = get_pages( $childargs );
	$childcount = count( $children );
	if( $childcount == 0 ) {
		$title = get_the_title( $post->ID );
		echo '<li>' . $title . '</li>';
	}
} // close foreach
?>