Sprinkle thyme, 1/4 teaspoon salt, 1/4 teaspoon pepper, and rosemary evenly over chicken. Dredge chicken in flour; shake off excess flour. Heat 1 1/2 teaspoons oil in a large skillet over medium-high heat. Add 4 chicken breast halves to pan; cook 2 minutes or until browned. Turn chicken over; cook 1 minute. Remove chicken from pan. Repeat procedure with remaining 1 1/2 teaspoons oil and remaining chicken. Arrange chicken in a single layer on the rack of a roasting pan coated with cooking spray; place rack in pan. Bake at 425° for 12 minutes or until a thermometer inserted into thickest part of chicken registers 160°. Remove from oven. Cover and let stand 10 minutes.
Heat a medium saucepan over medium-high heat. Coat pan with cooking spray. Add shallots to saucepan; sauté 30 seconds, stirring frequently. Stir in wine, scraping pan to loosen browned bits. Increase heat to high; bring to a boil. Cook 10 minutes or until wine is reduced to 1 cup. Add broth; cook 16 minutes or until broth mixture is reduced to 1/3 cup. Remove from heat; stir in remaining 1/4 teaspoon salt, remaining 1/4 teaspoon pepper, and sugar. Gradually add butter, stirring constantly with a whisk until smooth. Serve sauce with chicken.