Production method of E(2-Benzoyloxy)-1,4-cyclohexanedione mono-ethylene ketal contains 2 steps. The synthetic routes are as follows:

A. N-Methyl-O-benzoylhydroxylamine hydrochloride 1. (18.32 g, 150.0 mmol, 1 eq.) is placed in an open single-necked 500-mL round-bottomed flask equipped with a large magnetic stirrer and dissolved in 200 mL of methylene chloride. This clear solution is cooled to 0 °C in an ice-water bath before the controlled addition of carbonyldiimidazole (24.32 g, 150.0 mmol, 1 equiv.) over a period of five min. The ice bath is removed and the resultant yellow solution is stirred at ambient temperature until all effervescence has ceased (15 minutes). After this period, N-methylhydroxylamine hydrochloride (15.87 g, 190.0 mmol, 1.27 equiv.) is added in one portion to the reaction mixture and stirring is continued for a further 40 min at 25 °C. The reaction broth is diluted with 100 mL of methylene chloride, transferred to a 1-L separatory funnel and washed sequentially with cold (0 °C) 1 M hydrochloric acid (300 mL) and saturated sodium hydrogen carbonate solution (300 mL). The organic layer is separated, dried using sodium sulfate (40 g), filtered through a Büchner funnel and concentrated to dryness in a 500-mL round-bottomed flask on a rotary evaporator (25 °C, 20 mmHg). Diethyl ether (200 mL) is added to the resulting liquid followed by 4 M HCl in dioxane (75 mL, 0.30 mol, 2 equiv.). After 30 minutes, the solid precipitate is collected in a Büchner funnel, washed with 100 mL of ice-cold diethyl ether and dried under high vacuum (0.5 mmHg) for 8 h to give N-methyl-O-benzoylhydroxylamine hydrochloride 1 as a white microcrystalline solid (17.45 g, 62%) that is used in Step B without further purification.

B. (2-Benzoyloxy)-1,4-cyclohexanedione (mono)ethylene ketal 2. An open 25-mL single-necked round-bottomed flask equipped with a magnetic stirring bar is charged at ambient temperature with 1,4-cyclohexanedione mono-ethylene ketal (4.68 g, 30.0 mmol, 1 equiv.) and dimethyl sulfoxide (7.5 mL). N-Methyl-O-benzoyl-hydroxylamine hydrochloride 1 (5.63 g, 30.0 mmol, 1 equiv., as prepared above) is added to the flask over a period of 15 min and the reaction mixture is stirred for 1 h. The solution is subsequently poured into 300 mL of ethyl acetate and transferred to a 1-L separatory funnel where it is washed with 250 mL of water. The layers are separated and retained: the organic layer is washed further with two 250 mL portions of water, which are discarded; and the original aqueous layer is washed with two 100 mL portions of ethyl acetate which are added to the original organic layer. The combined organic fractions are dried using magnesium sulfate (25 g), filtered through a Büchner funnel and concentrated on a rotary evaporator (40 °C, 20 mmHg) to give a brown solid as a crude product. The crude solid is transferred to a 25-mL Erlenmeyer flask and dissolved in 5 mL of hot (80 °C) isopropyl alcohol, then allowed to slowly cool to room temperature. The resultant solid is collected in a Büchner funnel and sequentially washed with ice-cold isopropyl alcohol (50 mL) and ice-cold 35–60 petroleum ether (50 mL) before being dried under high vacuum (0.5 mmHg) for 8 h to yield (2-benzoyloxy)-1,4-cyclohexanedione mono-ethylene ketal 2 as pale yellow needles (6.38 g, 77%).