I have a upcoming Business Class award made through United.

Jax - IAD (Coach)
IAD - DUB (Business Class)
DUB - AMS (Coach)

I have 3-5 hr layovers at IAD & DUB.
I was wondering which if any lounges I would have access to without having to pay a fee? Since my flight from DUB - AMS is in Coach would I have lounges access for free in Dublin?

Some one mentioned as long as one leg of your reservation is in business class then for lounges access purposes, the coach legs would fall under the “Business Class” umbrella?