Thank you very much for your inquiry. The Garden Nurse, Susan Gruber, has provided the information below.

You describe classic symptoms of transplant shock. It is very common for plants to show some leaf drop and browning soon after planting. Most trees recover well - and although it may look a little rough for the rest of this season, chances are it will be just fine. If many more leaves turn brown and fall off, it may be worth calling the nursery where you purchased the plant and inquire about their return/replacement policy. Keep your receipt and document the appearance of the tree with some photos.
Here are some tips to help the tree establish:
Water the tree roots and the soil around the planting hole weekly unless there has been a soaking rain. More frequent watering can reduce root growth.
Place 3-4" of bark mulch over the root system, beginning an inch away from the trunk and extending 6" past the edge of the planting hole. Mulch is one of the best ways to provide the roots with the best growing conditions.
Do not fertilize until next spring.
Wait to prune off any leafless branches until next spring, then trim off any dead wood as soon as you see new leaves beginning to grow.

Again, thanks for the question and let me know if you have more.

Respectfully

Trey Rogers, The Briggs & Stratton Yard Doctor, YardDoctor.com