General procedure for the synthesis of 1-methylcyclopropane-1-carboxylic acid from 2,2-dichloro-1-methylcyclopropanecarboxylic acid: 6.9 g of sodium metal and 120 mL of anhydrous toluene were added to a 500 mL three-necked round-bottomed flask equipped with a mechanical stirrer under nitrogen protection. The oil bath was heated until the sodium metal was completely melted and the sodium sand was formed by rapid stirring. Subsequently, 100 mL of anhydrous tetrahydrofuran was added to the reaction system and 16.9 g (0.1 mol) of 2,2-dichloro-1-methylcyclopropanecarboxylic acid dissolved in 30 mL of ethanol/water (19:3, v/v) was slowly added. After dropwise addition, the reaction was continued with stirring at room temperature for 1 hour. After completion of the reaction, 50 mL of concentrated hydrochloric acid was slowly added dropwise under stirring to the reaction mixture pH=1 and stirring was continued for half an hour. The reaction mixture was extracted with dichloromethane, and the organic phase was dried and the solvent was removed by evaporation under reduced pressure to give 9.26 g of 1-methylcyclopropane-1-carboxylic acid in 92.6% yield and ≥95% purity.
