Is there any work around to install macOS Big Sur on a mid 2011 Imac?

Welcome to Apple Support Communities.

No. A 2011 iMac hasn't received an upgrade for 4 years now. The latest version for it is macOS High Sierra.

-Jack

Jack-19 has already provided you with the answer. The only "work around" is to get a newer iMac if you want to run macOS Big or Monterey when it comes out.