THE UNEXPECTED FORMATION OF A DITHIENOPYRONE (2,7-DIMETHYL-DITHIENO-[2,3-B-2',3'-D] PYRAN-4-ONE)

The reaction between the ambident anion of the 5-methyl 2-hydroxythiophene system with carbon disulfide and methyl iodide yielded, besides the expected 3- left bracket bis(methylthio)methylene right bracket -5-methyl-4-thiolene-2-one, 2,7-dimethyl-dithienol left bracket 2,3-b; 2',3'-d right bracket pyran-4-one. Its structure was proven by X-ray crystallography, and a reaction path for its formation is suggested. The analogous selenophene reacts similarly.