Sodium Hydroxide → 4-Methoxycarbonylcubanecarboxylic acid

Cubane-1,4-dicarboxylic acid dimethyl ester (3.10 g, 14.1 mmol) purchased from Enichem Sintesi SpA, was dissolved in 75 ml of hot methanol in a 250 ml, round-bottomed flask equipped with a condenser. Solid NaOH (ACS grade 0.560 g, 14.1 mmol) was added, and the reaction mixture was refluxed under N2 for 13-15 h, then cooled to room temperature. The reaction mixture was diluted with 120 ml of water and extracted with ether (1×75 ml, 3×25 ml). The combined organic layer was dried over Na2SO4, filtered, and concentrated, leaving 373 mg (12%) of recovered starting material. The aqueous layer was acidified to pH 3 with 6N HCl and then extracted with chloroform (4×50 ml). The combined organic phase was dried over sodium sulfate, filtered, and concentrated furnishing 2.25 g (77%) of 1-carboxy-4-carbomethoxycubane as a white powder having a melting point of 178°-179° C. An NMR spectrum of the product at 500 MHz, dissolved in deuterated chloroform, had peaks assigned the following sigma values: 4.27 ppm (multiplet, 6 hydrogens) and 3.71 ppm (singlet, 3 hydrogens).