1,3-Indandione (sometimes simply indanedione) is an organic compound with the molecular formula C6H4(CO)2CH2.

[4][5] Solid 1,3-indandione is a diketone, As a solution in water, it is partially (~2%) enolized.

The enolate anion exhibits significant delocalization, and the highest electron density is on the second carbon.

[citation needed] 1,3-Indandione can be prepared by decarboxylation of the sodium salt of 2-ethoxycarbonyl-1,3-indandione, which itself is obtained by Claisen condensation of ethyl acetate and dimethyl phthalate.

[citation needed] The carbon at the C-2 position is alpha to both carbonyls, and thus can act as a nucleophile.