Background and overview of the preparation method of 2-methyltetrahydrofuran
2-methyltetrahydrofuran is an important organic synthesis intermediate and solvent, a new material and application Fine chemical materials in the field. In organic synthesis, it is mainly used in the synthesis of chloroquine phosphate, primaquine phosphate, thiamine, etc. In terms of solvent application, 2-methyltetrahydrofuran is mainly used in the organic synthesis of resins, natural rubber, ethyl cellulose and chloroacetic acid-vinyl acetate copolymers.
As a cyclic ether and a Lewis base, 2-methyltetrahydrofuran is an environmentally friendly and unique solvent with excellent performance. In recent years, due to the excellent performance and environmentally friendly characteristics of 2-methyltetrahydrofuran, it has developed rapidly in the field of solvent replacement applications: ① Used to replace tetrahydrofuran, ether, etc. that have serious safety hazards, and used in Grignard reactions Solvent; ② Used to replace highly toxic halogenated hydrocarbons, benzene, etc. as reaction solvents or extraction solvents for organic synthesis; ③ Solvent used in organoboric acid-10B metal reactions and two-phase reactions.
2 – Preparation method of methyltetrahydrofuran Preparation
Among the existing methods, there are many methods for synthesizing 2-methyltetrahydrofuran. Depending on the starting materials and the selection of catalysts, they are mainly summarized as follows: ：
Preparation method of 2-methyltetrahydrofuran 1. Furfural as raw material
The main method of synthesizing 2-methyltetrahydrofuran using furfural as starting material It refers to a method in which furfural is reduced by catalytic hydrogenation to obtain 2-methylfuran (hereinafter referred to as MeF), and then MeF is catalytically hydrogenated to obtain 2-methyltetrahydrofuran. Among them, the main catalysts for catalytic hydrogenation of MeF to obtain 2-methyltetrahydrofuran are as follows:
(1) Nickel is usually used as a catalyst in industrial production. According to literature reports, the reaction yields of US patents US6479677, US6852868 and US7064222 are the best. When the MeF hydrogenation temperature is 100-130°C, the yield of 2-methyltetrahydrofuran obtained in this step is about 90%.
(2) In 1959, RaneyPd (5% Pd-Al alloy treated with NaOH to remove 40% to 50% of Al) was used to reduce 2-methylfuran, and the temperature was controlled at 150°C. , 100% 2-methyltetrahydrofuran can be obtained (DokladyAkadNaukSSSR, 1959, 125: 3345～3347). If the reaction is carried out at 275°C, 80% of 2-methyltetrahydrofuran will be obtained. At the same time, they also used 5% Pt-C and Ni-ZnO as catalysts to study the reaction mechanism of the nickel carbonate reaction (Doklady Akad Nauk SSSR, 1958, 122: 625-628.).
(3) Furfural undergoes Cannizzaro reaction or hydrogenation reverse reduction reaction to obtain furfuryl alcohol, which is then catalytically hydrogenated to synthesize 2-methyltetrahydrofuran. Furfuryl alcohol is hydrogenated and reduced to obtain 2-methyltetrahydrofuran. Under the conditions of 220℃ and 18.0MPa, 38.5% of 2-methyltetrahydrofuran can be obtained; at 160℃ and 18.0MPa, 11.5% of the product can be obtained; at 220℃ and 16.0 MPa, using 1:1 RaneyNi-Cu chromite as catalyst, 42% of the product can be obtained (Trudy Leningrad TekhnolInstIm Lensoveta, 1958, 44: 3-5). Advantages of this synthesis process: It is of certain value to use this reaction to conduct theoretical research, especially studying the effects of temperature and pressure on this reaction.
Preparation method of 2-methyltetrahydrofuran 2. Furfural derivatives as raw materials
In 1980, Baikova et al. used 5-methylfurfural as raw materials to prepare 2-Methyltetrahydrofuran. Using Pd-K2CO3 as a catalyst and controlling the temperature at 200 to 300°C, 5-methylfurfural mainly undergoes dehydroxylation reaction and hydrogenation reaction and is converted into 2-methyltetrahydrofuran.
Preparation method of 2-methyltetrahydrofuran 3. Diol as raw material
2-methyltetrahydrofuran, as a cyclic ether, can act as a catalyst It is obtained by intramolecular dehydration of diol. The more representative methods mainly include:
(1) In 1981, GeorgeA reported a fast and effective dehydration reaction using Nafion-H (a solid super acid perfluorosulfonic acid resin catalyst) As a catalyst, the yield can be as high as 90% after reacting at 135°C for 5 hours, and the by-products are easy to separate, the catalyst is easy to regenerate, and the reaction does not require a solvent (Synthesis, 1981, 6: 474-476.).
(2) Kuramoto et al. dehydrated 2-methyl-1,4-butanediol in the presence of aliphatic tertiary amine to prepare 2-methyltetrahydrofuran. In this way, 2-methyl-1,4-butanediol, Bu3N and hydrochloric acid were heated and stirred at 130°C for 6 hours to obtain 99% of the product (JP: 02167274).
(3) In 1980, Gojkovic et al. used o-hydroxyl groups to participate in the formation of intramolecular cyclic ethers. This reaction involves the intramolecular Markovikov reaction of some acyclic enols in the hydroxymercuration-demercuration reaction to generate cyclic ethers (GlasHemDrusBeograd, 1980, 45(11): 497-506.).
Preparation method of 2-methyltetrahydrofuran 4. Lactone, acid anhydride or diester as raw material
2-methyltetrahydrofuran can also be produced through lactone , anhydride or diester reduction reaction to prepare. For example, in the presence of SiHCl3, irradiation of lactone with γ-rays or ultraviolet light or γ-rays produced by 60Co at 3×105r/h can produce 2-methyltetrahydrofuran with a yield of 82.3%. The advantages of this synthesis method are: short one-step reaction process and fast reaction speed.
Preparation method of 2-methyltetrahydrofuran 5. Use other raw materials to prepare 2-methyltetrahydrofuran
(1) Under 14KPa, use MeCO( CH2)nCH2Cl is used as raw material and reacts with Bu3SnH to obtain cyclic ether, and the yield is related to the size of the ring. When n=2, the yield of 2-methyltetrahydrofuran is 98% (JOrganometChem, 1985, 287(1):49～56.).
(2) Ismailova uses RCH2CH2OCHR’CH2R (R=Br, Cl; R’=H, Me) in a polar solvent to generate molecules under the action of zinc powder, potassium amalgam or lithium amalgam. Internal coupling reaction yields 2-methyltetrahydrofuran.
(3) Use aqueous Cu(II) alkali metal chloride to catalytically oxidize 1,3-pentadiene to obtain 2-methyltetrahydrofuran.
References
[1][China invention, China invention authorization] CN200910095661.6 A green synthesis method of 2-methyltetrahydrofuran
