To 4,4-bis(ethoxycarbonyl)heptanedioic acid (23.6 g, 78 mmol) was added the compound in 100 mL of a premixed 10% (v/v) solution of pyridine and acetic anhydride. The reaction mixture was placed in a preheated oil bath heated to reflux with continuous stirring for 3 hours. After completion of the reaction, it was cooled to room temperature and concentrated under reduced pressure. The resulting oil was azeotropized twice with 95% ethanol (300 mL) and water (300 mL) and subsequently treated with solid potassium carbonate (12.9 g, 93.6 mmol). Concentrated under reduced pressure to remove ethanol, the remaining aqueous layer was diluted to redissolve the solid and then extracted with ether (2 x 150 mL). The organic phases were combined, dried over magnesium sulfate, and filtered. The filtrate was concentrated under reduced pressure to afford 4-oxo-1,1-cyclohexanedicarboxylic acid 1,1-diethyl ester (11.82 g, 48.8 mmol, 62.9% yield) as an amber-colored oil.HPLC analysis showed a retention time of 2.00 min (AP 74%); 1H NMR (500 MHz, CDCl3) δ ppm 4.24 (4H, q, J = 7.12 Hz), 2.44 (4H, t, J=6.56 Hz), 2.37 (4H, t, J=6.41 Hz), 1.27 (6H, t, J=7.17 Hz).
