108384-35-6

25662-28-6

108384-35-6

Experimental Procedure - Part 1: Step 1 - Oxidation of Carboxymethylcyclopentene: Procedure: To a 2L round bottom flask (pre-cooled to 0°C) equipped with a magnetic stirrer and internal thermometer was added acetic anhydride (615g, 570mL, 6.02mol). Under continuous stirring and controlled exothermic conditions, chromium trioxide (214 g, 2.14 mol) was added in batches. The resulting dark red solution was stirred until the chromium trioxide was completely dissolved and the temperature was reduced to 20 °C. A 5L three-necked flask was equipped with a dropping funnel, a top stirring device, a nitrogen inlet and an internal thermometer and a solution of methyl cyclopentene-1-carboxylate (100g, 101mL, 0.793mol) dissolved in 1.4L of dichloromethane was added to it. The prepared oxidized solution of chromium trioxide and acetic anhydride was transferred to a dropping funnel and slowly added dropwise to the reaction mixture, ensuring that the internal temperature was maintained at 10-14 °C. At the beginning of the dropwise addition, the reaction solution was gradually darkened from yellow color. Due to laboratory equipment limitations, the reaction was carried out in two batches, and each batch was operated as follows: the dark, homogeneous solution obtained from the reaction was carefully transferred to a 4L beaker fitted with an overhead stirrer. The reaction flask was rinsed with 250 mL of dichloromethane and the washings were combined. 500mL of water was added to the reaction mixture followed by slow addition of 10g of sodium bicarbonate and gas release was observed. The remaining sodium bicarbonate (830 g, 10 mol) was added in batches with the stirring rate maintained at 500 rpm. The dark green suspension obtained was diluted with 1 L of water and filtered through a 3 L sintered funnel fitted with a 1 cm Solka-Floc pad. The filtrate was extracted with dichloromethane (3 x 1 L), the organic phases were combined and dried with anhydrous magnesium sulfate, filtered and concentrated under reduced pressure to give a light green oil. The oil was distilled through a 30 cm Vigreux column and recrystallized with methyl tert-butyl ether:hexane (1:10, total volume 55 mL) to give 38.4 g of methyl 3-oxocyclopent-1-enecarboxylate (35% yield) as a white crystalline solid.