18915-70-3Relevant articles and documents
Directing abilities of alcohol-derived functional groups in the hydroformylation of olefins
Ren, Li,Crudden, Cathleen M.
, p. 1746 - 1750 (2002)
The hydroformylation of allylic and homoallylic alcohols and their derivatives using cationic and neutral rhodium complexes has been examined. The highest diastereoselectivity (87:13) was observed in the reaction of 1-methoxymethoxy-2-methylenecyclohexane. Higher yields and similar selectivities were obtained in the reaction of the TBDMS-protected alcohol. The major diastereomer results from hydroformylation syn to the functional group, which would suggest a directing effect. However, hydroformylation of 3-methylene-1-cyclohexanol derivatives occurs on the face opposite to the directing group in the major isomer. These data, in addition to the results of hydroformylation of 1-methyl-2-methylenecyclohexane, suggest that inherent conformational preferences are of significant importance in determining the product distribution and that the directing power of simple alcohols and their derivatives is moderate at best under the conditions examined in this study.
Silica-Promoted Diels-Alder Reactions in Carbon Dioxide from Gaseous to Supercritical Conditions
Weinstein, Randy D.,Renslo, Adam R.,Danheiser, Rick L.,Tester, Jefferson W.
, p. 2878 - 2887 (2007/10/03)
Amorphous fumed silica (SiO2) was shown to increase yields and selectivities of several Diels-Alder reactions in gaseous and supercritical CO2. Pressure effects on the Diels-Alder reaction were explored using methyl vinyl ketone and penta-1,3-diene at 80°C. The selectivity of the reaction was not affected by pressure/ density. As pressure was increased, the yield decreased. At the reaction temperature, adsorption isotherms at various pressures were obtained for the reactants and the Diels-Alder adduct. As expected when pressure is increased, the ratio of the amount of reactants adsorbed to the amount of reactants in the fluid phase decreases, thus causing the yield to decrease. The Langmuir adsorption model fit the adsorption data. The Langmuir equilibrium partitioning constants all decreased with increasing pressure. The effect of temperature on adsorption was experimentally determined and traditional heats of adsorption were calculated. However, since supercritical CO2 is a highly compressible fluid, it is logical to examine the effect of temperature at constant density. In this case, entropies of adsorption were obtained. The thermodynamic properties that influence the real enthalpy and entropy of adsorption were derived. Methods of doping the silica and improving yields and selectivities were also explored.
