14686-14-7Relevant articles and documents
Chemistry and Kinetics of Dipropylcarbene in Solution
Tae, Eunju Lee,Zhu, Zhendong,Platz, Matthew S.,Pezacki, John Paul,Warkentin, John
, p. 5336 - 5342 (1999)
The photochemistry of 2-methoxy-2-methyl-5,5-dipropyl-Δ3-1,3,4-oxadiazoline (1a) and 2,2-dimethoxy-5,5-dipropyl-Δ3-1,3,4-oxadiazoline (1b) was investigated. Photolysis (300 nm) of these compounds in solution leads to fragmentation to 4-diazoheptane (major), which slowly forms the corresponding azine. Fragmentation to form 4-heptanone is also observed. Yields of 4-diazoheptane in CH2Cl2 are much larger than those in pentane. 4-Diazoheptane can be trapped with 1-pentene to form a pyrazoline or with methanol to form 4-methoxyheptane. The pyrazoline can be decomposed photochemically to form 1,1,2-tripropylcyclopropane. In solution, 4-diazoheptane is inefficiently photolyzed to dipropylcarbene (DPC), which can be trapped with piperidine or with pyridine in laser flash photolysis experiments. Analysis of the piperidine and pyridine data indicates that the lifetime of DPC in cyclohexane, methylene chloride, or Freon-113 (CF2ClCFCl2) solution at ambient temperature is controlled by 1,2 hydrogen migration to form Z- and E-3-heptene. The lifetime deduced under these conditions is ≈300 ps, which is about 20-fold shorter than that of dimethylcarbene in perfluorohexane at ambient temperature. Upon photolysis (254 nm) of oxadiazoline 1a in argon, 4-diazoheptane and 1-methoxydiazoethane are formed. These diazo compounds undergo subsequent photolysis that revealed the formation of methoxy(methyl)carbene and E- and Z-3-heptene. It was not possible to detect DPC in argon at 14 K.
Designing bifunctional alkene isomerization catalysts using predictive modelling
Landman, Iris R.,Paulson, Erik R.,Rheingold, Arnold L.,Grotjahn, Douglas B.,Rothenberg, Gadi
, p. 4842 - 4851 (2017/10/23)
Controlling the isomerization of alkenes is important for the manufacturing of fuel additives, fine-chemicals and pharmaceuticals. But even if isomerization seems to be a simple unimolecular process, the factors that govern catalyst performance are far from clear. Here we present a set of models that describe selectivity and activity, enabling the rational design and synthesis of alkene isomerization catalysts. The models are based on simple molecular descriptors, with a low computational cost, and are tested and validated on a set of eleven known Ru-imidazol-phosphine complexes and two new ones. Despite their simplicity, these models show good predictive power, with R2 values of 0.60-0.85. Using a combination of principal components analysis (PCA) and partial least squares (PLS) regression, we construct a "catalyst map", that captures trends in reactivity and selectivity as a function of electrostatic charge on the N? atom, EHOMO, polar surface area and the optimal mass substituents on P/distance Ru-P ratio. In addition to indicating "good regions" in the catalyst space, these models also give insight into mechanistic steps. For example, we find that the electrostatic charge on N?, EHOMO and polar surface area are crucial in the rate-limiting step, whereas the optimal mass of substituents on P/distance Ru-P is correlated with the product selectivity.
Graphite oxide activated zeolite NaY: Applications in alcohol dehydration
Todd, Alexander D.,Bielawski, Christopher W.
, p. 135 - 139 (2013/03/29)
A mixture of graphite oxide (GO) and the zeolite NaY (Si/Al = 5.1) was used to dehydrate various alcohols to their respective olefinic products. Using conditions optimized for 4-heptanol (15 wt% GO-NaY (1 : 1 wt/wt), 150°C, 30 min), a series of secondary and tertiary aliphatic alcohols were cleanly dehydrated in moderate to excellent conversions (27.5-97.2%). Several primary alcohols were also dehydrated, although higher catalyst loadings (200 wt% GO-NaY (1 : 1) and longer reaction times (3 h) were required. The enhanced dehydration activity was attributed to the ability of GO to convert NaY to an acidic form and without the need for ammonium cation exchange and/or high temperature calcination. The Royal Society of Chemistry 2013.
