Searching for unknowns across an internal library or database can serve as a major time saver. A more accessible database is the Internet. Many chemists and elucidators search the World Wide Web using a mass, a molecular formula or a fragment.
Be aware that proprietary data sent over the Internet runs the risk of being intercepted.
Searching the Internet via Google™ for the molecular formula C17H11N5 produced 787 hits with Letrozole appearing in the first dozen hits or so. Using a variation of the molecular formula C17 H11 N5 with the elements spaced out produced over 34,000 hits without any clear reference to Letrozole.