Naphthalene-1,8-dithiol reacted with aldehydes to give dithioacetals which were oxidized to 2-substituted naphtho[1,8-de]1,3-dithiin-1-oxides (4). 2,2-Disubstituted naphtho[1,8-de]1,3-dithiin-1-oxides (5) were obtained on treatment of 4 with NaH/electrophiles. Photolysis of 4 and 5 undergoes intramolecular oxygen rearrangement to generate aldehydes and ketones quantitatively together with naphthalene-1,8-dithiole.