Water → 1-Methyl-3-methylidenecyclobutane-1-carboxylic acid

To a solution of KOH (12.0 g, 213 mmol) in water (10 mL) and EtOH (10 mL) was added 1-methyl-3-methylidenecyclobutanecarbonitrile (53.3 mmol, crude) and the resulting solution was heated to reflux for 2.5 hrs. The mixture was cooled to rt and the solvent was removed under vacuum. The residue was diluted with water (30 mL) and washed with EtOAc (30 mL). The aqueous layer was acidified with concentrated HCl to pH˜1 in ice bath, and then extracted with EtOAc (two×30 mL). The combined organics were dried over MgSO4 and concentrated to give the title compound acid as pale brown liquid. 1H NMR (400 MHz, chloroform-d) δ ppm 4.90 (quin, J=2.41 Hz, 2H), 3.16-3.34 (m, 2H), 2.54 (qd, J=2.10, 16.57 Hz, 2H), 1.49 (s, 3H).