Are there any movie actor/actress turned into porn actor/actress? [closed]

Many did, most of them did due to lack of work:

Maitland Ward: she was in Boy Meets World and The Bold and the Beautiful but from 2019, she is working in pornographic films.

She told In Touch Weekly: "They asked me to be a part of this, and I thought, 'I never knew there was anything in adults or porn or whatever that was this well done'.

"I read the script, and I was like, 'This is really, really well written. This has so many themes in this and just my character is so different than anything I have portrayed before'." - mirror.co.uk

Jaimee Foxworth: Child actor from Family Matters did work in pornographic films from 2000-2002, she told her reasons:

“Work stopped coming in and my family fell on hard times, so I started doing things that probably weren’t the best decision for a young woman,” - lifeandstylemag

Then there are some edge cases too like Dustin Diamond who only gave his face in pornographic film, rest was body double.

Few more names are present in cheatsheet and lifeandstylemag.

Also from Wikipedia: List of mainstream actors who have appeared in pornographic films