8-Fluoro-1,4-dioxaspiro[4.5]dec-7-ene synthesis

Yield:142273-44-7 92%

Reaction Conditions:

with diethylamino-sulfur trifluoride;1,8-diazabicyclo[5.4.0]undec-7-ene in dichloromethane at 10 - 25; for 12 h;Reagent/catalyst;Solvent;

Steps:

3.1 (a) Synthesis of 8-fluoro-1,4-dioxaspiro[4.5]dec-7-ene

312 g of dichloromethane, DBU (456.6 g, 3.0 mol, 3.0 eq) were successively1,4-cyclohexanedione monoethylene glycol ketal (156.2 g, 1.0 mol, 1.0 eq) was added to a 1000 ml three-neck reaction flask.Stirring was turned on, the temperature was lowered to 10±5°C, and DAST (193.4 g, 1.2 mol, 1.2 eq) was added dropwise.The internal temperature is controlled at 10±5°C. After the dropwise addition is completed, the temperature is increased by 5°C per hour, and the temperature rises to 25°C.And reacted at 25 °C for 12 hours. The GC controls the progress of the reaction.When the GC control monitors the integrated peak area of the raw material on the GC spectrum/(integral area of the raw material peak+integral area of the product peak)<0.5%, that is, the GC control monitors the remaining amount of the reaction raw material to be less than 0.5%. reaction,The raw material here refers to 1,4-cyclohexanedione monoethylene ketal,The product here refers to 8-fluoro-1,4-dioxaspiro[4.5]dec-7-ene.After the reaction was completed, the reaction solution was slowly added to 750 g of ice water to separate the organic phase.The aqueous phase is extracted three times with 312 g of methylene chloride (the total amount of methylene chloride is 312 g x 3) and all organic phases are combined.Wash with hydrochloric acid (750g, 1mol/L) several times. The GC controls the organic phase without DBU residue.The organic phase is then washed several times with 750 g of saturated sodium bicarbonate until the pH is 7-8.After drying over anhydrous sodium sulfate and filtering, the organic phase filtrate was concentrated under reduced pressure to obtain a crude product. The crude product was subjected to vacuum distillation. When the temperature was raised to 80°C, the fraction was started to receive 145 g of a product.The resulting product was subjected to gas chromatography (GC) and nuclear magnetic resonance (HNMR) detection.To determine its structural formula and purity.From the NMR spectrum, the product obtained was identified as 8-fluoro-1,4-dioxaspiro[4.5]dec-7-ene.The purity was 98.2% by GC and the calculated yield was 92%.

References:

CN107827721,2018,A Location in patent:Paragraph 0059-0062; 0070-0075; 0082-0085; 0092;