Preheat the oven to 425°. Spread the pecans in a pie plate and toast for about 6 minutes, until fragrant; let cool slightly.
Meanwhile, spray a 12-cup muffin tin with cooking spray. In a food processor, pulse the flour with 2 tablespoons of the sugar, the baking powder, baking soda and salt. Add the cubed butter and pulse until it is the size of small peas. Add the buttermilk and pulse a few times, just until a soft dough forms. Turn the dough out onto a floured surface and knead 3 times. Pat or roll the dough into an 8-by-12-inch rectangle. Brush with 2 tablespoons of the melted butter.
In a small bowl, combine the remaining 2 tablespoons of sugar with the cinnamon and sprinkle all over the dough. Beginning at a long side, roll the dough into a tight cylinder and pinch the seam closed. Cut the dough into 12 slices.
Divide the maple syrup and the remaining 2 tablespoons of melted butter among the cups. Scatter the pecans in the cups and top with the dough pinwheels. Bake for about 18 minutes, until golden; place a baking sheet below to catch any drips. Invert a rack over the rolls and invert them onto the rack. Replace any pecans that get stuck in the cups and let cool for 5 minutes before serving.