Vilenchik et al. ^[8] proposed that hexafluoropropene is oxidized to prepare hexafluoropropylene epoxide. Hexafluoropropylene epoxide could react with hexafluoropropene under room temperature catalyzed by cesium fluoride. This method with high molecular utilization but low reactive selectivity could give C₆F₁₂O, accounting for approximately 35%. Furthermore, the yield could be enhanced to approximately 50–70% using halogen-like potassium salts (i.e., KOCN, KSCN, KCN) as a catalyst and the acetonitrile as a solvent (SU698289). Hexafluoropropylene epoxide and hexafluoropropene could react through a gas phase reaction under a catalysis of cesium fluoride with activated carbon as the carrier, and the yield of C₆F₁₂O could be improved to more than 90% (RU2010150091A). However, the raw materials of this method are uncommon and the reaction yield in actual production is less than the theory. The by-product, hexafluoropropylene dimer, is difficult to separate and the reaction selectivity needs to be enhanced.

Zapevalov et al. ^[9] reported a method to prepare C₆F₁₂O through the oxidation rearrangement reaction for hexafluoropropylene dimer. Hexafluoropropylene dimer has two isomers including perfluoro-4-methyl-2-pentene and perfluoro-2-methyl-2-pentene. Additionally, two kinds of corresponding epoxides could be obtained from hexafluoropropylene dimer under the oxidation of sodium hypochlorite. The epoxides could be converted into C₆F₁₂O using cesium fluoride or trimethylamine, which is mild and could give 93% yield. This process includes multiple reactions, the yields of which need to be improved so that it could be practically used in the industry.

Compared with perfluoro-2,3-epoxy-4-methyl pentane, the epoxidation of perfluoro-2,3-epoxy-2-methyl pentane gives only one product, which is more suitable for the preparation of C₆F₁₂O. However, oligomerization of hexafluoropropylene mainly gives perfluoro-4-methyl-2-pentene. Additionally, it is now very significant in the industry to produce perfluoro-2-methyl-2-pentene through isomerization of perfluoro-4-methyl-2-pentene. The patent of 3M company (WO1995025082A1) disclosed a method for preparing C₆F₁₂O using perfluoro-2-methyl-2-pentene as a raw material through multi-step reactions, such as epoxidation by sodium hypochlorite and catalysis by cesium fluoride. Based on this, researchers (CN103508868B) have designed and optimized the reaction route: (1) isomerization from perfluoro-4-methyl-2-pentene to obtain perfluoro-2-methyl-2-pentene, (2) epoxidation to obtain perfluoro-2,3-epoxy-2-methyl pentane, and (3) catalysis to obtain C₆F₁₂O. In the optimization study of this method ^[10], the yield of C₆F₁₂O could reach more than 95%, which shows the prospective of the method. The patent (CN105198719B) disclosed a one-step preparation of C₆F₁₂O through the gas-phase reaction under the conditions of oxidizing gas and catalyst. This process requires only one step reaction with no solvent, reducing the pollution and cost.

The reaction of hexafluoropropylene and perfluoropropionyl fluoride as raw materials under the conditions of alkali metal fluoride catalyst in aprotic polar solvent, diglyme or acetonitrile is also the main method for C₆F₁₂O synthesis ^[11]. 3M company (WO2001005468A2) disclosed the reaction conditions: diglyme as the solvent and active potassium fluoride as the catalyst, 70 °C, 1 MPa pressure in their patent. This reaction with high selectivity gives a C₆F₁₂O 90.6% yield. However, the raw material, perfluoropropionyl fluoride is highly corrosive, which is difficult to prepare and store. In addition, the reaction needs to be carried out under a higher pressure, and the entire process has high requirements on the material of the reactor. Fenichev et al. ^[12] proposed that perfluoropropionyl fluoride can be easily obtained by isomerization of hexafluoropropene oxide using alkali metal fluorides, KF and CsF, with the same conditions of C₆F₁₂O synthesis. They found that the water content in acetonitrile is the main factor resulting in the deactivation of the catalyst and the methods of isolating C₆F₁₂O from the reaction mixture by hydrolysis, and subsequent hydrogenation on the palladium catalyst supported on the activated carbon could lead the target product with a purity of 99.95 wt%. They also designed and created the pilot setup for production. Sha et al. ^[13] discussed the synthesis process of perfluoropropionyl fluoride. They produced hexafluoropropylene oxide through liquid phase oxidation of hexafluoropropylene as raw material using molecular oxygen, and then obtained the final product after isomerization using a bubbling reactor, which seems to be an ideal reaction route for industrial production.

All these three synthesis routes for C₆F₁₂O use hexafluoropropylene as the raw material. Some problems exist in these routes in that they all have certain side reactions, and the by-products are difficult to separate from major products. Moreover, the purity of the product should be paid more attention. There are various kinds of fluoride involved in the synthesis of C₆F₁₂O, and the toxicity of different fluorides varies greatly. If these substances are not effectively separated, even very small amounts of toxic impurities exist in the final product, the toxicity for the product of C₆F₁₂O will be totally different. It is urgent to optimize the synthesis routes and look for a safe, green, high yield, low in cost, less impurity and continuous synthesis routes for industrial production.