Replace curly quotes with straight quotes

I’m trying to replace curly quotes. I added the following to my theme’s function.php but it doesn’t seem to be working? Any ideas? Thanks.

function removesmartquotes($content) {
$content = str_replace(““”, “"”, $content);
$content = str_replace(“””, “"”, $content);
$content = str_replace(“‘”, “'”, $content);
$content = str_replace(“’”, “'”, $content);
$content = str_replace(“″”, “"”, $content);

$content = str_replace(““”, “"”, $content);
$content = str_replace(“””, “"”, $content);
$content = str_replace(“‘”, “'”, $content);
$content = str_replace(“’”, “'”, $content);
$content = str_replace(“—”, “–“, $content);
$content = str_replace(“…”, “…”, $content);

return $content;
}
add_filter(‘the_title’, ‘removesmartquotes’);
add_filter(‘the_excerpt’, ‘removesmartquotes’);
add_filter(‘the_content’, ‘removesmartquotes’);