No - one of the main points of a hash is that it is non-reversible.

Also, if you had a short string that could be expanded into the larger key, then what you really have is a short key to a slightly different crypto system, which is less secure than the original key in the original system.

Also, if you can significantly compress a string of truly random data, you can also probably compress digital video by a significant factor as well, and should therefore found a startup selling your groundbreaking compression technology.