In a large mixing bowl, stir together the brown sugar, butter, pumpkin spice, and vanilla. Next, stir in the cinnamon, pretzels, and pecans until well combined.
1/2 cup light brown sugar, 1/4 cup butter, melted, 2 tsps pumpkin pie spice, 1 tbsp vanilla extract, 3 cups Cinnamon Chex cereal, 2 cups mini pretzels, 1 cup pecan halves