4H-?Pyrrolo[1,?2-?b]?pyrazole-?2-?carboxylic acid, 5,?6-?dihydro-

86477-09-0

796729-03-8

General Steps: Example 162a 5,6-dihydro-4H-pyrrolo[1,2-b]pyrazole-2-carboxylic acid 162a To a 25 mL round-bottomed flask equipped with a reflux condenser was added ethyl 5,6-dihydro-4H-pyrrolo[1,2-b]pyrazole-2-carboxylate (540 mg, 3.0 mmol), 2 N aqueous sodium hydroxide solution (3.5 mL), and 1,4-dioxane (3.0 mL). The reaction mixture was heated to reflux at 65 °C for 2.5 hours. Upon completion of the reaction, the system was cooled to room temperature and the pH was adjusted to 2-3 with concentrated hydrochloric acid.The precipitated solid was collected by filtration to afford the target product 162a (260 mg, 57% yield) as a yellow solid.MS-ESI: [M + H]+ 153.3.