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Step 1: Preparation of 3-methylenecyclobutanecarboxylic acid Potassium hydroxide (264 g, 4.7 mol) was added to a mixed solution of 3-methylenecyclobutanecarbonitrile (110 g, 1.18 mol) in ethanol (500 mL) and water (500 mL), and the resulting mixture was heated to reflux overnight. Upon completion of the reaction, ethanol was removed by distillation under reduced pressure. The remaining solution was cooled to below 10 °C and acidified with concentrated hydrochloric acid to pH 1. The mixture was extracted with ethyl acetate (2 × 500 mL), the organic phases were combined and dried over anhydrous sodium sulfate. The organic phase was concentrated under reduced pressure to give the title compound 3-methylenecyclobutanecarboxylic acid (132 g, 100% yield) as a yellow oil.

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