I planted mine so they have afternoon shade, and they survived through last summer ... all but two died when the frost got them in late November, and those are still growing and setting fruit again. :)

They will probably stop setting fruit in the hottest part of the summer, but will resume when it cools off.

I had some tomatoes in full sun a couple years back and kept them alive all summer with whatever % shade cloth the big blue box store carries (60% if I remember correctly). Since then I've planted in afternoon shade and not worried about it. I think I read that the tomato pollen becomes infertile at 95 degrees, and it's proven pretty true in my experience. You'll continue getting flowers up to 105 or so, but no fruit sets. After that they go dormant, look a little wilty, and perk back up once the summer temperatures drop.