and morpholine‐2,5‐dithiones 11, respectively, depending on the reaction conditions. The structures of 3aa, 4aa, 10a, and 11a were established by X‐ray crystallography. All attempts to prepare S‐containingmorpholine‐2,5‐dione analogs or thiomorpholine‐2,5‐diones by cyclization of corresponding S‐containing precursors were unsuccessful and led to various other products. The structures of some of them