It is always risky to buy expensive furniture in a home where cats live. If
the sofa is made of real leather, the smell will be irresistible to the
cats. But, of course you can train them. If you, from day one, tell them not
to scratch the sofa, they will learn after a while. A simple and strong
"NO!" combined, maybe, by a squirt of water from a bottle, will do the
trick. BTW, declawing is NOT a solution!

Good luck, and keep in mind: Cats rule the house, furniture doesn't...

We just got two new cats from shelters, one is a kitten and one is three,
and neither of them have scratched our leather living room furniture.  They
aren't interested in it at all.  I have heard that cats don't like the
texture of leather for scratching.  IOW, you may not even have a problem.

Dawn

My cat ignores the leather couch apart from sitting on it with his people.

My experience has been the opposite of those who have already replied.
My cats ruined my leather chair. The problem is that when they jump
down from the chair, they put out their claws. That puts holes in the
seat of the chair.

I do not know how they put the long scratches onto the seat, but it
was typical cat scratch looking marks. Bottom line in my experience is
that cats and leather did not mix well for me.

I do have a scratching post, I do trim their back claws properly and
they are front declawed.