Green Bean Chicken Salad

1/3 cup red wine vinegar or cider vinegar
1/4 cup minced fresh basil or 4 teaspoons dried basil
2 teaspoons granulated sugar
1/8 teaspoon salt
1 tablespoon plus 2 teaspoons olive or canola oil, divided
1 pound boneless skinless chicken breasts, cubed
1 pound fresh green beans, trimmed
2 plum tomatoes

In a large bowl, whisk the first 4 ingredients and 1 T. of the oil; set aside. In a nonstick skillet, saut