My DD stopped napping somewhere between 2 and 2 1/2. It was pretty gradual. For a while, she would be every other day. On the days she napped, she would go to bed late and sleep later the next day and therefore not need a nap that day. But she would go to bed earlier, wake up early, and need a nap again.
Now she is 3, and if she does nap any time after 12 she will be up until at LEAST 10 if not much later. I prefer the no nap and a guarantee to be asleep at 8.
If it is a struggle to get him to sleep, I think he probably doesn't need it. Maybe try a quiet time instead, with stories or time alone, etc. and see if that works.