Simple preparation of epimeric 2,6-dimethyl-4-(N′-substituted thioureido)-1,3-dioxanes and crystal structure of rel-2S,4S,6S-2,6-dimethyl-4-(N′-benzylthioureido)-1,3-dioxane

✍ Scribed by Juraj Bernát; Ladislav Kniežo; Gabriela Birošová; Ján Imrich; Jaroslav Podlaha; Miloš Buděšínský; Jaromír Novák; Tibor Liptaj

• Publisher: Elsevier Science
• Year: 1991
• Tongue: French
• Weight: 647 KB
• Volume: 47
• Category: Article
• ISSN: 0040-4020
• DOI: 10.1016/s0040-4020(01)86472-3

✦ Synopsis

One-pot reaction of acetaldehyde, KSCN and POCl3 affords 2,6dimethyl-4-isothiocyanato-1,3dioxane 4 in good yield. Compound 4 reacts with primary amines to give crystalline re/-2S,4R,6S-2,6dimethyl-4-(N'substituted thiourefdo)-1,3dioxanes 5. The obtained thioureas 5 with axial thioureido group are spontaneously epimerised in acetone solution under formation of re/-2S,4S,6S-2.6dimethyl-4-(N'-substituted thioureido) 1,Jdioxanes 6. These compounds form dimers containing relatively strong intermolecular hydrogen bonds -N-H...S-as confirmed by X-ray diffraction analysis. Treatmenat of isothiocyanate 4 with secondary amines is accompanied by epimerisation during the reaction and leads to a mixture of diastereoisomeric 5 and 6 or to pure diastereoisomers 6.