There are a variety of synonyms for the phrase "not to be expected". Some possible options include "unanticipated", "unexpected", "surprising", "unforeseen", "unexpectedly", "out of the blue", "not foreseen", "unpredictable", "anomalous", "startling", "strange", and "bizarre". These terms all convey a sense of surprise or shock, indicating that something has happened that was not previously planned or anticipated. Whether used in casual conversation or in formal writing, these synonyms can help to convey a sense of drama or urgency when discussing unexpected events or situations.