RewriteBase /
RewriteCond %{THE_REQUEST} ^[A-Z]{3,9}\ /([^.]+)\.html\ HTTPS
RewriteRule ^([^.]+)\.html$ sitename.com/$1 [R=301,L]
RewriteCond %{REQUEST_URI} !(\.[^./]+)$
RewriteCond %{REQUEST_fileNAME} !-d
RewriteCond %{REQUEST_fileNAME} !-f
RewriteRule (filename1|filename2|filename3) /$1.html