- Preparation method of 2-methyl-1,3-pentadiene
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The invention relates to a preparation method of 2-methyl-1,3-pentadiene. The preparation method comprises the following steps: in the presence of a supported metal catalyst and a catalyst assistant,carrying out a dehydration reaction on 2-methyl-2,4-pentanediol to obtain 2-methyl-1,3-pentadiene. According to the method, strong acid is not used as a catalyst, so the selectivity of a product is effectively improved, higher yield can be obtained, the problem of equipment corrosion is avoided, the service life of equipment is prolonged, environmental protection benefits are remarkable, and the method is environment-friendly. The 2-methyl-1,3-pentadiene prepared by the method is high in selectivity and high in yield, the generation of a byproduct, namely 4-methyl-1,3-pentadiene is effectivelyreduced, the cyclic application of the catalyst is realized, and the industrial large-scale production of ligustral is facilitated.
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Paragraph 0041-0043; 0049-0051
(2020/11/26)
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- Method of preparing 2-methyl-1, 3-pentadiene
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The invention discloses a method of preparing 2-methyl-1, 3-pentadiene, which comprises the following steps: by using isobutene and acetaldehyde as raw materials, carrying out a Prins reaction to prepare 4-methyl-3-ene-2-pentanol and 4-methyl-4-ene-2-pentanol, and carrying out a dehydration reaction to prepare 2-methyl-1, 3-pentadiene. The whole reaction process is mild in condition, low in cost,low in energy consumption and less in three wastes, and the total yield of the 2-methyl-1, 3-pentadiene after the two-step reaction is higher than the yield of the 2-methyl-1, 3-pentadiene prepared byadopting 2-methyl-2, 4-pentanediol dehydration in a traditional process.
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Paragraph 0076-0122
(2020/04/17)
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- A process for preparing 2 - methyl - 1, 3 - pentadiene method (by machine translation)
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A process for preparing 2 - methyl - 1, 3 - pentadiene method, relates to 2 - methyl - 1, 3 - pentadiene. The 2 - methyl - 2, 4 pentanediol remove one molecule of water, to obtain the 4 - methyl - 4 - pentene - 2 - ol; the 4 - methyl - 4 - pentene - 2 - ol to remove a water molecule, to obtain 2 - methyl - 1, 3 - pentadiene. The 2 - methyl - 1, 3 - pentadiene yield, 2 - methyl - 1, 3 - pentadiene and 4 - methyl - 1, 3 pentadiene ratio can be increased to 9:1, 2 - methyl - 1, 3 - pentadiene and production yield is greater than 80%. The use of weakly acidic catalyst, to reduce the loss of the device. Selecting mild catalyst, to reduce the loss of the device, improves the reaction environment-friendly. The method of dewatering step by step, the reaction greatly reduces the 4 - methyl - 1, 3 pentadiene generation, improves the 2 - methyl - 1, 3 pentadiene yield. (by machine translation)
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Paragraph 0018; 0021-0023; 0024; 0027-0029; 0030; 0033-0035
(2019/06/30)
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- Method for preparing ligustral
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The invention provides a method for preparing ligustral. The method comprises the following steps: preparing 2,4,4,6-tetramethyl-1,3-dioxane, preparing 2-methyl-1,3-pentadiene, and synthesizing the ligustral. The whole reaction process is gentle in condition, nearly free of side effect, short in time and low in energy consumption, the total yield of the ligustral of the three steps of reaction is greater than 87%; the 2,4,4,6-tetramethyl-1,3-dioxane is prepared in a first step, and the yield is greater than 98%; the 2-methyl-1,3-pentadiene is prepared in a second step, and the yield is greater than 96%; the ligustral is synthesized in a third step, and the yield is greater than 94%; small molecules such as isobutene and acetaldehyde which are low in price and easy to obtain are adopted as raw materials, a process route for preparing the 2-methyl-1,3-pentadiene is innovated, steps such as condensation and dehydration which are high in cost and low in yield in a conventional process are avoided, and the cost of the method is reduced by about 40% when being compared with that of a conventional process.
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Paragraph 0008; 0026; 0031; 0034; 0037; 0040; 0045; 0046
(2017/08/29)
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- Process for dehydrating 2-methylpentane-2,4-diol
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A process for dehydrating 2-methylpentanediol-2,4 to a mixture of 2-methyl-1,3-pentadiene and 4-methyl-1,3-pentadiene at elevated temperature in the presence of an acid catalyst using a polyglycol ether as a heat carrier, wherein a polyglycol ether containing from 80 to 100% by weight of a polyethylene glycol dimethyl ether of the formula CH3(OCH2CH2)nOCH3 where n=2-8 and from 0 to 20% by weight of a polyethylene glycol monomethyl ether of the formula CH3(OCH2CH2)nOH where n=2-8 based in each case on the total mass of polyglycol ether, is used.
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Page/Page column 2-3
(2008/06/13)
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- On the regiochemistry of cyclialkylation of regiodefined 4-halo-1-alkenylmetals producing cyclobutenes
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A combination of recently developed anti-carbometallation of homopropargyl alcohols and cyclialkylation of 4-halo-1-alkenyllithiums of appropriate stereochemistry and regiochemistry provides, for the first time, a regiospecific procedure for the synthesis of regiodefined cyclobutenes presumably via σ-type cyclialkylation, whereas carboalumination of 4-halo-1-alkynylmetals containing Si or Al leads to regioconvergent cyclobutene formation.
- Liu, Fang,Negishi, Ei-ichi
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p. 1149 - 1152
(2007/10/03)
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- Isomerisation des radicaux insatures. III. Radicaux α,α,β-, α,β,γ- et α,α,γ-trimethallyles
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α,α,β-, α,β,γ-, and α,α,γ-trimethallyl radicals have been generated in the 147.0-nm gas phase photolysis of 2,3,3-trimethyl-1-butene, 3,4-dimethyl-2-pentene, and 2,4-dimethyl-2-pentene, respectively.Under these conditions, the majority of allyl radicals have an internal energy sufficient for further decomposition: they give rise to the formation of various 1,3-dienes and small amounts of either 1,2- or 2,3-dienes.An internal sigmatropic 1,2-hydrogen atom transfer process is part of the proposed mechanism to explain such products.Moreover, the fragmentation of the trimethyl substituted allyl radicals involves the split of one β(C-C) bond, then one β(C-H), and, to a lesser extent, one central C-CH3 bond.
- Deslauriers, Helene,Collin, Guy J.
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p. 3168 - 3173
(2007/10/02)
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