hydrocyanation of styrene


The catalyst performance in this process still needs to be improved in terms of activity, especially for the hydrocyanation of 3PN, and, in selectivity for both hydrocyanation steps. Reproduced from Matsumoto, K.; Oguma, T.; Katsuki, T. Angew. This approach was validated using advanced chemometrics. Scheme 4. Several ligands have been applied in this reaction and their influence on activity, regio- and enantioselectivity has been considered. Cyclopropanation using Co-porphyrin complex and tosyldiazomethane. The application of new tetraphenol-based diphosphite ligands (TP) in the hydrocyanation reaction is described in Chapter 4. Figure 3. Uninhibited HCN should be stored at a temperature lower than its melting point (−13 °C). According to the literature4, 6 these are among the most efficient ligands for this reaction. The selective stabilization of this intermediate in the presence of the Lewis acid leads to Full geometry optimizations and saddle‐point searches were all performed using the Gaussian 03 program.23 The full‐electron 6‐31+G(d) basis set was used for the nickel ion, whereas all atoms of the styrene molecule, HCN, and Lewis acids (AlCl3 and CuCN) were described by the 6‐311+G(d,p) basis set. 1-Phenyl-1,3-butadiene, 1-vinyl-3,4-dihydronaphthalene, and 1-vinylindene undergo highly regioselective hydrocyanation under ambient conditions to give exclusively the 1,2-adducts in good to excellent yields. Up to 83 % of the linear product 3‐phenylpropionitrile was obtained by applying phosphite ligands in the presence of AlCl3. Struktur und Reaktivität später Übergangsmetall‐ η3‐Benzylkomplexe. gratefully acknowledges The Netherlands Organization for Scientific Research (NWO‐CW) for financial support. Moreover, the introduced a C1-symmetric salan ligand 44, which can be readily prepared from proline, for the titanium-catalyzed asymmetric epoxidation of styrene derivatives (Scheme 20).87 The titanium catalyst shows excellent enantioselectivity ranging from 96% to 98% ee, regardless of the substituents. Moreover, the somewhat stronger binding of the CuCN co‐catalyst in the intermediate shifts the equilibrium of the process towards the formation of the branched nitrile. Arenes 131 react with pinacolborane in the presence of rhodium and iridium catalysts such as Cp*Rh(η4-C6Me6) <2000JA12868, 2001OL2831>, CpIrPMe3 <1999JA7696>, and [RhClP(Pri)3]N2 <2001AGE2168> to afford aryl boronates 132. The selective stabilization of this intermediate in the presence of the Lewis acid leads to the formation of a {"}steady state{"} for the ¿3-benzyl intermediate and indirectly promotes the formation of the linear product 3-phenylpropionitrile via the s-alkyl intermediate. According to present knowledge, this reaction leads predominantly to the branched product 2-phenylpropionitrile (98%). Experimental section 150 5.9. A. Elshabini, F. Barlow, in Encyclopedia of Materials: Science and Technology, 2001. Very recently, living polymerization was achieved for the first time using a SnCl4/base initiating system.147 For example, IBEA–EtAlCl2 or IBEA–TiCl4/SnCl4 polymerized 6-t-butoxy-2-vinylnaphthalene (tBOVN) in a controlled fashion in CH2Cl2 in the presence of ethyl acetate or 1,4-dioxane at –30 °C. Furthermore, the computed activation free energy (ΔG#,solv) for the former elementary reaction step is lower by 15 kJ mol−1 than that for the latter one. The corresponding catalytic cycles towards the formation of linear and branched products both in the presence and absence of Lewis acid are schematically illustrated in Figure 2 b. We thank NWO‐NCF and SARA for computational time on the IBM p575 Huygens supercomputer. The boronate ester complex further reacts with ethylene to yield B-vinyl catechol boronate ester 137 albeit in low conversion rate. The energy difference for the binding of the Lewis acid to various positions of the phenyl ring does not exceed 7 kJ mol−1 and, hence, a substituent effect does not seem to play a significant role. The major change in the qualitative thermodynamic picture due to the implication of the more realistic catalytic cycle (Scheme 4 b) was observed in the relative stabilities of the direct products of the reductive elimination, 9 a and 9 b (Figure 2 b). The selective stabilization of this intermediate in the presence of the Lewis acid leads to Give an example of how enantioselectivity of a reaction generally is reported, with its meaning. This is due to the higher basicity of the anionic CN group in the [L2Ni(H)CN] species compared to that in the covalently bound free HCN and nitrile species. C.M. This approach was validated using advanced chemometrics. Interestingly, such a species has never been reported before for the hydrocyanation of vinylarenes. K. Matyjaszewski, in Encyclopedia of Materials: Science and Technology, 2001. Therefore, the effect of the AlCl3 Lewis acid on the thermodynamics of the corresponding catalytic cycles (Figure 2 b) was analyzed by means of DFT calculations. Another excellent initiating system is DME–TiCl4/SnCl4 with ethyl acetate (an added base) and DTBP (a proton trap).112,113 This system also produced finely controlled polymers (Mw/Mn ∼ 1.1) of pMOS, tBOS, and pMSt in CH2Cl2 at 0 °C. Enantioselective catalysts that have been applied to hydroformylation of styrenes often show low selectivity for that of vinyl acetate or allyl cyanide. Thus, AlCl3 has a dual role in the catalytic hydrocyanation of styrene. Since the hydrocyanation of 3PN proceeds via s-alkyl intermediates and the first two steps of the DuPont process via the p-allyl species, these results provide an explanation for the observed catalytic activity. Taking into account the above discussion on the role of the Lewis acid in the regioselectivity in the styrene hydrocyanation, it is expected that the difference between AlCl3 and CuCN is mainly due to the less pronounced selective stabilization of the η3‐benzyl 8 b intermediate upon interaction with the CuCN Lewis acid and the different relative stabilities of the intermediate reaction products (9 a,b)Cu. The Ni‐catalyzed hydrocyanation of styrene‐d8 was carried out in both the presence and absence of AlCl3 with P(OPh)3 as ligand. b) A more complex reaction scheme reflecting the mechanistic details of the catalytic reaction. The complex 5 and the active species 6 are in equilibrium (ΔGsolv= +2 kJ mol−1). B. E H. (K 12 7 1 3 4 1 (N 9. The nickel‐catalyzed functionalization of alkenes with HCN1 is an important industrial application of homogeneous catalysis. Atomic charges were computed with the NBO method as implemented in the Gaussian 03 program package. View the article PDF and any associated supplements and figures for a period of 48 hours. Chelating phosphorus ligands with a rigid backbone and a large natural bite angle were applied in the nickel-catalysed hydrocyanation of styrene. Electronic DFT‐computed energies provided in the text were all corrected for zero‐point vibrations. Within the postulated thermodynamic cycle it is considered that the introduction of the AlCl3 species takes place at this step. The preference for the formation of the Al⋅⋅⋅O interaction over the Al⋅⋅⋅P interaction is probably due to the fact that the Lewis acid AlCl3 binds more strongly to the “hard” oxygen atom rather than to the “softer” phosphorus atom.17 In agreement with the DFT‐computed free energy changes, 31P NMR spectroscopy indicates that the addition of styrene to [Ni(AlCl3)(bippp)(cod)] does not displace the AlCl3 from the oxygen atom. This new catalyst could be the key towards process intensification in the future. Table 2. The polymer end groups can be transformed to other functional groups, such as alcohols or amines, and a range of polymers with different architectures and compositions can be prepared by relatively simple means. Complex 6 is chosen as the zero level for the free energy diagrams (b) and (c). This approach was validated using advanced chemometrics. The catalytic results are presented in Table 1. In all cases, IBEA–EtAlCl2 (initiator)/SnCl4 (activator) and an added base produced polymers with very narrow MWDs (Mw/Mn = 1.03–1.13), although the rate differences (from 20 s to over 200 h for completion of the polymerization) were significant.139 It should be emphasized that SnCl4, when combined with a base, is invariably effective for achieving living cationic polymerization of various St derivatives, as opposed to EtAlCl2, which was not able to induce well-controlled polymerization of all monomers but p-chlorostyrene (pClSt) even in conjunction with an added base. Jaundice has been seen in people repeatedly exposed to small amounts of the solvent [113]. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. The spectra were analyzed comprehensively to obtain conversion profiles from the different band dynamics. So far, this reaction did not attract much attention, due to the lower conversion generally obtained as compared to the hydrocyanation of 1,3-dienes and vinylarenes. Pemirolast 7 was prepared in a one-pot reaction of 2-amino-3-methylpiperidine, malononitrile, and HC(OEt)3 and NaN3 in AcOH at 90 °C, followed by treatment of the reaction mixture with conc. A. Ford, A.R. Many investigations are also focusing on the hydrocyanation of vinylarenes. Reaction of 2-aminopyridines with formaldehyde and electron-rich α-substituted styrenes permitted the synthesis of 4-substituted 4-phenyl-3,4-dihydro-2H-pyrido[1,2-a]pyrimidines <1996TL2615>.

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