Lilacs are sun lovers. Yours will never be happy where you planted it. I would replace it with shrub that can live in the shade. You may try a hydrangea paniculata or Hydrangea arborescens. There are many varieties available. Best And Happy Yardening, Nancy.
Susan, That is old time recipe that folks used to use and swore by. Worth a try, but I don't think it will make up for the lack of sun. Please let us know of your success. Best Nancy