2(5H)-furanone in the Vilsmeier - Haak reaction. Synthesis of β-substituted furans. Molecular structures of 3-dimethylaminomethylene-5-formyl-2(3H)-furanone and dimethylammonium 3,5-di(2,2-dimethyl-4,6-dioxo-1,3-dioxan-5-ylidenemethyl)-2-furanolate

The reaction of 2(5H)-furanone with the Vilsmeier - Haak - Arnold reagent and subsequent addition of concentrated aqueous HClO4 to the reaction mixture give (3-dimethylaminomethylen-2-oxo-3H-5-ßtranyl)melhylenimmonium perchlorate, whose hydrolysis under various conditions leads to 3-dimethylaminomethylene-5-formyl-2(3H)-furanone or to the potassium salt of 5-hydroxy-2,4-furandicarbaldehyde. The reaction of these products with CH-acids was studied. The structures of the key compounds of this work have been proved by the method of X-ray diffraction analysis. ©1999 KluwerAcademic/Plenum.