The reaction was carried out overnight at reflux in 2N KOH aqueous solution using 2,2-dimethyltetrahydro-2H-pyran-4-carbonitrile (900 mg, 6.47 mmol) as raw material. After completion of the reaction, the reaction mixture was diluted with water and extracted with ethyl acetate and the organic phase was discarded. The aqueous phase was acidified to pH < 7 with 2N HCl solution and subsequently extracted twice with ethyl acetate. The organic phases were combined, dried with anhydrous sodium sulfate, filtered and concentrated in vacuum to give the crude product 2,2-dimethyltetrahydro-2H-pyran-4-carboxylic acid (889 mg, 5.62 mmol, 87% yield). The product was characterized by 1H-NMR (400 MHz, DMSO-d6): δ[ppm] 1.13 (s, 3H), 1.14 (s, 3H), 1.26-1.45 (m, 2H), 1.65-1.73 (m, 2H), 2.59 (tt, 1H), 3.54 (td, 1H), 3.60 (ddd, 1H), 12.20 (s, 1H).
