Synthesis and Crystal Structure of 3,3,6,6-Tetramethylmorpholine-2,5-dione, and Its 5-Monothioxo and 2,5-Dithioxo Derivatives

✍ Scribed by Nasser Mawad; Fatemeh Ghorbani-Salman Pour; Anthony Linden; Heinz Heimgartner

• Publisher: John Wiley and Sons
• Year: 2010
• Tongue: German
• Weight: 360 KB
• Volume: 93
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.201000318

✦ Synopsis

The synthesis of 3,3-dimethylmorpholine-2,5-diones 4a was achieved conveniently via the direct amide cyclization of the linear precursors of type 3, which were prepared by coupling of 2,2-dimethyl-2H-azirin-3-amines 2 with 2-hydroxyalkanoic acids 1. Thionation of 4a with Lawessons reagent yielded the corresponding 5-thioxomorpholin-2-ones 10 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-containing morpholine-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 have also been established by X-ray crystallography.