926-56-7Relevant academic research and scientific papers
Preparation method of 2-methyl-1,3-pentadiene
-
Paragraph 0041-0043; 0049-0051, (2020/11/26)
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.
Direct Olefination of Alcohols with Sulfones by Using Heterogeneous Platinum Catalysts
Hakim Siddiki,Touchy, Abeda Sultana,Kon, Kenichi,Shimizu, Ken-Ichi
, p. 6111 - 6119 (2016/04/26)
Carbon-supported Pt nanoparticles (Pt/C) were found to be effective heterogeneous catalysts for the direct Julia olefination of alcohols in the presence of sulfones and KOtBu under oxidant-free conditions. Primary alcohols, including aryl, aliphatic, allyl, and heterocyclic alcohols, underwent olefination with dimethyl sulfone and aryl alkyl sulfones to give terminal and internal olefins, respectively. Secondary alcohols underwent methylenation with dimethyl sulfone. Under 2.5 bar H2, the same reaction system was effective for the transformation of alcohol OH groups to alkyl groups. Structural and mechanistic studies of the terminal olefination system suggested that Pt0 sites on the Pt metal particles are responsible for the rate-limiting dehydrogenation of alcohols and that KOtBu may deprotonate the sulfone reagent. The Pt/C catalyst was reusable after the olefination, and this method showed a higher turnover number (TON) and a wider substrate scope than previously reported methods, which demonstrates the high catalytic efficiency of the present method. Olefination of alcohols: The first heterogeneous catalytic terminal and internal olefination of primary alcohols and methylenation of secondary alcohols with sulfones, a reusable carbon-supported Pt catalyst, and KOtBu is reported (see scheme).
Z-selective metathesis homocoupling of 1,3-dienes by molybdenum and tungsten monoaryloxide pyrrolide (MAP) complexes
Townsend, Erik M.,Schrock, Richard R.,Hoveyda, Amir H.
supporting information; experimental part, p. 11334 - 11337 (2012/09/05)
Molybdenum or tungsten monoaryloxide pyrrolide (MAP) complexes that contain OHIPT as the aryloxide (hexaisopropylterphenoxide) are effective catalysts for homocoupling of simple (E)-1,3-dienes to give (E,Z,E)-trienes in high yield and with high Z selectivities. A vinylalkylidene MAP species was shown to have the expected syn structure in an X-ray study. MAP catalysts that contain OHMT (hexamethylterphenoxide) are relatively inefficient.
Process for dehydrating 2-methylpentane-2,4-diol
-
Page/Page column 2-3, (2008/06/13)
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.
Gas-phase kinetic and mechanistic studies of some interconverting alkylcyclopropene pairs: Involvement of dialkylvinylidene intermediates and their quantitative behaviour
Graf Von Der Schulenburg, Wilhelm,Hopf, Henning,Walsh, Robin
, p. 1963 - 1979 (2007/10/03)
The pyrolyses of two isomeric pairs of alkylcyclopropenes, namely 1,3-dimethyl- (15) and 1-ethyl-cyclopropene (16), and 1,3,3-trimethyl- (5) and 1-isopropyl-cyclopropene (17), have been studied in the gas phase. Complete product analyses at various conversions up to 95% were obtained for the decomposition of each compound at five temperatures over a 40°C range. The time-evolution data showed that the isomerisation reactions 15?16 and 5?17 were occurring. Kinetic modelling of each system allowed the determination of rate constants for these and all other decomposition processes. Tests confirmed that all reactions were unimolecular and homogeneous. Arrhenius parameters are reported for overall reactions and individual product pathways. Further kinetic analysis allowed us to extract the propensities (at 500 K) for 1,3-C-H insertion of the dialkylvinylidene intermediates involved in the rearrangements as follows: kprim:ksec: ktert = 1:16.5:46.4. Additional experiments with 13C-labelled cyclopropenes yielded alkyl group migration aptitudes for the dialkylvinylidenes (from the pattern of 13C in the alkyne products) as follows: Me:Et:iPr=1:3.1:1.5. Explanations for these trends are given. Another important finding is that of the dramatic rate enhancements for 1,3-diene product formation from the 1-alkylcyclopropenes; this can be explained by either hyperconjugative stabilisation of the vinylcarbene intermediates involved in this pathway, or their differing propensities to 1,2 H-shift. The observed large variations in product distribution amongst these four cyclopropenes is interpreted in terms of these specific effects on individual pathways.
Catalytic hydromagnesation of di- and polymethyl-substituted 1,3-butadienes
Viktorov,Zubritskii
, p. 1755 - 1765 (2007/10/03)
Hydromagnesation of di- and polymethyl-substituted 1,3-butadienes with alkylmagnesium halides in the presence of Ni(PPh3)2Cl2 and NiPy4Cl2 was studied.
(E)- And (Z)-1-(Phenylsulfonyl)-4-(trimethylsilyl)-2-butenes: Synthetic Equivalents for the 1-(1,3-Butadienyl) Anion and the 1,1-(1,3-Butadienyl) Dianion
Meagher, Timothy P.,Yet, Larry,Hsiao, Chi-Nung,Shechter, Harold
, p. 4181 - 4192 (2007/10/03)
(E)- and (Z)-1-(phenylsulfonyl)-4-(trimethylsilyl)-2-butenes (7 and 8) are converted by n-BuLi to (E)- and (Z)-1-lithio-1-(phenylsulfonyl)-4-(trimethylsilyl)-2-butenes (15 and 16) with retention of initial stereochemistries. Reactions of 15 and 16 with electrophiles (protio and deuterio acids, primary, secondary, and benzyl halides, chloroformates, chlorothioformates, acid chlorides, epoxides, trialkylsilyl chlorides, and triethylgermanyl chloride) in THF or THF/HMPA give the corresponding (E)- and (Z)-1-(phenylsulfonyl)-1-substituted-4-(trimethylsilyl)-2-butenes (32) with stereochemical retention. That β,γ-unsaturated silyl sulfones 32 are formed instead of their α,β-unsaturated (conjugated) isomers are attributed to stabilizing multiple anionic and cationic hyperconjugation and to steric effects as in 29-31. Of importance in synthesis is that 32 are eliminated by TBAF at -20 to 0°C, thermally, or by column chromatography to (E)- (100 to > 93%) rather than (Z)-1-substituted-1,3-butadienes (38). Further, 32 undergo conversions by n-BuLi and various alkylating agents to (unconjugated) 1-(phenylsulfonyl)-1,1-disubstituted-4-(trimethylsilyl)-2-butenes (46) with retention of stereochemistry. Eliminations of 46 by fluoride ion, acid catalysis, or heat yield 1,1-disubstituted-1,3-butadienes (53). Silyl sulfones 7 and 8 are thus synthetic equivalents for the (E)-1-(1,3-butadienyl) anion (44) and the 1,1-(1,3-butadienyl) dianion (57). Silyl sulfones 7 and 8 also undergo efficient stereospecific intramolecular conversions by n-BuLi and α,ω-dihalides to 1,1-cycloalka-1-(phenylsulfonyl)-4-(trimethysilyl)-2-butenes (62 and 71) that are eliminated by fluoride ion, heat, or adsorption chromatography to 1,1-cycloalka-1,3-butadienes (72).
Gas-phase pyrolysis of several aliphatic 1,3-diols. The kinetic and mechanism of 2,4-dimethyl-2,4-pentanediol
Chuchani,Dominguez,Rotinov,Martin
, p. 851 - 854 (2007/10/03)
Satisfactory kinetic determinations of several aliphatic 1,3-diols were difficult to obtain. Moreover the product distributions from each of these substrates suggest complex parallel mechanisms. However, the elimination kinetic of 2,4-dimethyl-2,4-pentanediol has been measured over the temperature range of 419.7-459.9 °C and pressure range of 47-115 torr. The reaction carried out by employing a static system, in seasoned vessel, and in the presence of the free-radical inhibitor propene, proved to be homogeneous, unimolecular, and follows a first-order rate law. The products are acetone, isobutene, and H2O. The rate coefficient is expressed by the following Arrhenius equation: log k1(s-1) = (12.53±0.58)-(217.3±8.0) kJ mol-1 (2.303 RT)-1. The pyrolytic elimination of this substrate is believed to proceed through a concerted six-membered cyclic transition-state type of mechanism.
On the regiochemistry of cyclialkylation of regiodefined 4-halo-1-alkenylmetals producing cyclobutenes
Liu, Fang,Negishi, Ei-ichi
, p. 1149 - 1152 (2007/10/03)
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.
Polylithiumorganic compounds - 23. 1: 3,4-dilithio-1,2-butadienes by addition of lithium metal to 1,4-unsymmetrically substituted butatrienes
Maercker, Adalbert,Wunderlich, Hans,Girreser, Ulrich
, p. 6149 - 6172 (2007/10/03)
The synthesis of the highly reactive 1,4-unsymmetrically substituted butatrienes 12a-c is described. When employing a strict synthetic protocol, these alkatrienes react with lithium metal to 3,4-dilithio-1,2-butadienes 20a-c as stable intermediates. The structure of 20 is supported by IR and NMR spectroscopic evidence. The same dianionic intermediate can be prepared in one case by double deprotonation of the 1,2-butadiene 19. Upon derivatization, either 3,4-disubstituted 1,2-butadienes 24, 2,3-disubstituted 1,3-butadienes 25, or 1,4-disubstituted 2-butynes 26 are formed, depending on the nature of the electrophile employed. Copyright
