I live in downtown Toronto. The bush is in full sun against my front porch. There is a small garden it is part of and then a grass front. The miniature lilac bush was dug up from another garden last fall and transferred to my front garden. It sprouted leaves and small lilac flowers this spring. In the past month all the leaves have begun to curl and are now dried up. Is it dying?
Your bush may have been getting insufficient water. Transplanted shrubs and trees, even small ones, need a great deal of water to establish new root systems in their first year. It is now quite hot in Toronto and you say it is planted in the full sun against your front porch. You also say all the leaves are dead. I’m not sure if the shrub is dead. Lilacs are really quite hardy. I would advise watering it deeply twice a week – slowly pour out one pail of water each time. It may take a month or more of doing this, but I think new leaves will appear.