PHILADELPHIA — In back-to-back sales this December, Freeman’s presents American Art Week, bringing the best of American Art to market, with a strong emphasis on 20th-century canvases. Led by striking paintings by Robert Henri, Bo Bartlett and William Glackens, American Art Week offers important, fresh-to-market works, including two curated single-owner selections. Absentee and Internet live bidding will be available through LiveAuctioneers.