Ok so this is a very silly question which I should definitely know the answer to by year 3 of my PhD...

Is it ok to introduce new literature in the discussion chapter of my thesis? For example when comparing findings from other studies? I don't have to had mentioned the comparative study in lit review chapter in the start of my thesis right? because otherwise I would be randomly listing a load of literature in my lit review just to be able to cite it in my discussion chapter.

Thanks for your time and hopefully not laughing at my naivety!

I'm not sure if there are any 'hard and fast' rules for whether you should do it or not, but I have included some new references in my Results and Discussion chapter in the same manner you have: comparing my results and findings with those of other studies (I have also included a handful in my Conclusions chapter, but literally only 2-3, and only as a signpost for future research I might do, eg. "Bob and Smith found xyz by doing abc, so in future it could be beneficial to try a slightly modified abc in this project to see if it resolves issues 123").

I would probably avoid bringing in TOO many new resources though. If there are a lot of similar studies you want to mention, I'd suggest maybe putting some in the Lterature Review or Methodology chapters or whatever and then just mentioning some of the more recent ones in your Discussion/Results.