Thiourea was oxidized in the presence of potassium permanganate to yield formamidine disulfide. This was then reacted with various aldehydes to yield formamidine disulfide Schiff bases. Each Schiff base was then condensed with maleic and phthalic anhydride to give corresponding seven-membered heterocyclic ring derivatives respectively. The structures were identified by their uncorrected melting point, FT-IR spectra and mass spectra fragmentation pattern.