SQLite execution order, brackets not working

Im trying to select rows from a table, union the result with another select statement and then order that by timestamp. Unfortunately it only orders the second select statement with this command:

SELECT message, transmitter_ename , Timestamp, didread FROM messages WHERE transmitter_ename= ? AND receiver_ename= ? UNION ALL SELECT message,transmitter_ename , Timestamp,  didread FROM messages WHERE transmitter_ename= ? AND receiver_ename=? ORDER BY Timestamp ASC

I tried to use brackets but SQLite doesn't accept those(Error undefined).

I couldn't find anything related to that on the web.

Cheers, Valentin