Alkenes Catalyzed by Ni complexes

The Institut Franqais du Petrole has developed and commercialized a process, named Dimersol X, based on a homogeneous catalyst, which selectively produces dimers from butenes. The low-branching octenes produced are good starting materials for isononanol production. This process is catalyzed by a system based on a nickel(II) salt, soluble in a paraffinic hydrocarbon, activated vyith an 

The reaction takes place at low temperature (40-60 °C) in a series of weU-mixed reactors (two or more, up to four). The pressure is chosen to maintain all reactants and products in the liquid phase (no gas phase). Mixing and heat removal are 

Despite all the advantages of this process, one main limitation is the continuous catalyst carry-over by the products, with the need to deactivate it and dispose of wastes. One way to optimize catalyst consumption and waste disposal is to operate the reaction in a biphasic system. The first difliculty was to choose a good solvent. N,N-Dialkylimidazolium chloroaluminate ionic liquids proved to be the best candidates. They are liquid at the reaction temperature, butenes are reasonably soluble in them (Table 5.4-3), and they are poorly miscible with the products (Table 5.4-2, case (a)). The chloroaluminate eSiciently dissolves and stabilizes the nickel catalyst in the ionic medium without the addition of special ligand. The ionic liquid plays the role of both catalyst solvent and co-catalyst. Its Lewis acidity can be adjusted to get the best performance. The catalytically active nickel complex is generated directly in the ionic liquid by reaction of a commercialized tiickel(II) salt, as used in the Dimersol process, with an alkylaluminum chloride derivative. 

The biphasic system has been evaluated in terms of activity, selectivity, recyclability and lifetime of the ionic liquid, in a continuous flow pilot operation. A representative industrial feed (Raffinate II), composed of 70 wt.% butenes (27% of which is 1-butene) and 1.5 wt.% isobutene (the remainder being n-butane and isobutane) enters continuously into the well mixed reactor containing the ionic liquid and the nickel catalyst. Injection of fresh catalyst components can be made to compensate for the detrimental effects of random impurities present in the feed and for a slight catalyst carryover by the organic phase. The reactor is operated 

Despite the utmost importance of physical limitations such as solubility and mixing efficiency of the two phases, an apparent first-order reaction rate relative to the olefin monomer was determined experimentally. It has also been observed that an increase in the nickel concentration in the ionic phase results in an increase in the olefin conversion. 

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Tsuda and coworkers350 used nickel(O) complexes to effect the [2 + 2 + 2] cycloadditions between two alkyne units and one alkene unit and employed this strategy to synthesize copolymers. Thus, the reaction of diyne 602 with A-octylmaleimide (603) catalyzed by Ni(CO)2(PPh3)2 afforded copolymer 604 with a maximum yield of 60% and a GPC molecular weight of as high as 35,000, which corresponds to n = 64 (equation 172). The exo,exo-bicyclo[2.2.2]oct-7-ene moiety of 604 arises through the reaction of the initially formed [2 + 2 + 2] adduct with another equivalent of A-octylmaleimide. 

The hydrocyanation of 1-hexene catalyzed by [Ni P(OPh)3 4] has been studied.600 Isomerization of the alkene accompanies the reaction. Best rates were obtained in the presence of excess P(OPh)3 and a Lewis acid (ZnCl2). The excess P(OPh)3 was believed to suppress the formation of the cyano complex [Ni(CN)2 P(OPh)3 2], which does not catalyze hydrocyanation. ZnCl2 increases... 

It has been shown that the addition of HCN to the alkene occurs in a cis (suprafacial) manner.601 This was achieved by the addition of DCN to (E)- -deuterio-3,3-dimethylbut-l-ene, catalyzed by [Ni P(OPh)3 4] (131) (equation 162). This requires retention of configuration at the alkyl carbon atom during the reductive elimination of the product from the intermediate nickel(II)-alkyl complex. A cyanoalkyl complex [Ni(CN)(CHDCHBut) P(OPh)3 2] was proposed as the key intermediate in this process. 

The parent five-membered nitronate having no substituent at the 3-position was too unstable to be isolated. However, 3-substituted derivatives were highly stabilized. Especially, the 3-ethyl derivatives having a terminal electron-withdrawing substituent are readily available by the dehydrochlorination of 3-chloro-l-nitropropane in the presence of electron-deficient alkenes. It was our delight that the reaction of 3-al-kyl-substituted five-membered nitronates was also successfully catalyzed by R,R-DBFOX/Ph-Ni(SbFg)2 complex to at room temperature. This reaction was highly endo-selective (cisjtrans= 91 9) and enantioselective for the endo cycloadduct (92% ee). 

Unlike the case of the Ni-catalyzed reaction, which afforded the branched thioester (Eq. 7.1), the PdCl2(PPh3)3/SnCl2-catalyzed reaction with 1-alkyne and 1-alkene predominantly provided terminal thioester 6 in up to 61% yield in preference to 7. In 1983, a similar hydrothiocarboxylation of an alkene was also documented by using a Pd(OAc)2/P( -Pr)3 catalyst system with t-BuSH to form 8 in up to 79% yield (Eq. 7.6) [16]. It was mentioned in the patent that the Pt-complex also possessed catalyhc activity for the transformation, although the yield of product was unsatisfactory. In 1984, the hydrothiocarboxylation of a 1,3-diene catalyzed by Co2(CO)g in pyridine was also reported in a patent [17]. In 1986, Alper et al. reported that a similar transformation to the one shown in Eq. (7.3) can be realized under much milder reaction conditions in the presence of a 1,3-diene [18], and the carboxylic ester 10 was produced using an aqueous alcohol as solvent (Eq. 7.7) [19]. 

The reaction of alcohols with CO was catalyzed by Pd compounds, iodides and/or bromides, and amides (or thioamides). Thus, MeOH was carbonylated in the presence of Pd acetate, NiCl2, tV-methylpyrrolidone, Mel, and Lil to give HOAc. AcOH is prepared by the reaction of MeOH with CO in the presence of a catalyst system comprising a Pd compound, an ionic Br or I compound other than HBr or HI, a sulfone or sulfoxide, and, in some cases, a Ni compound and a phosphine oxide or a phosphinic acid.60 Palladium(II) salts catalyze the carbonylation of methyl iodide in methanol to methyl acetate in the presence of an excess of iodide, even without amine or phosphine co-ligands platinum(II) salts are less effective.61 A novel Pd11 complex (13) is a highly efficient catalyst for the carbonylation of organic alcohols and alkenes to carboxylic acids/esters.62... 

Ni(II) complexes of cyclam and oxocyclam derivatives catalyze the epoxidation of cyclohexene and various aryl-substituted alkenes with PhIO and NaOCl as oxidants, respectively. In the epoxidation catalyzed by the Ni(II) cyclam complex using PhIO as a terminal oxidant, the high-valent nickel- complexes (e.g., LNiin-0, LNi=0, LNiin-0-... 

HCN adds more readily to alkynes than to alkenes.179 The addition of HCN to acetylene catalyzed by Cu+ ions was once a major industrial process to manufacture acrylonitrile carried out in the presence of copper(I) chloride, NH4CI, and HC1180 (see Section 6.2.4). Zerovalent Ni and Pd complexes are effective catalysts... 

It appears likely that transient metallacyclobutanes are involved in a variety of organic reactions which are catalyzed by transition metal complexes. Thus, cycloadditions of activated alkenes to strained hydrocarbons such as quadricyclane and bicyclo[2.1.0]pentane are catalyzed by complexes such as Ni(CH2=CHCN)2 and probably involve initial formation of a nickelacyclobutane (Scheme 2) (79MI12200). The nature of the organometallic intermediates in related metal-catalyzed rearrangements (72JA7757) and retro-cyclo-addition reactions (76JA6057) of cyclopropanoid hydrocarbons, e.g. bicyclo[n.l.O]alkanes, has been discussed. 

Epoxidation of alkenes by Oj. This epoxidation can be effected with 02 and a reductant when catalyzed by a bis( 1,3-diketonato)nickel(II) complex. Reductants can be a primary or secondary alcohol2 or, preferably, an aldehyde (which is converted to an acid.3 The most efficient catalyst is Ni(dmp)2, although Ni(acac)2 is almost as... 

The complexes [Ni(acrylonitrile)2] and [Ni(COD)2] catalyze [3 + 2] cycloadditions of (26) with electron deficient l,2 isubstituted alkenes to afford 2,3- or 3,4-disubstituted methylenecyclopentanes such as (32) and (33). Similar reactions have been reported by use of tertiary phosphine complexes of nickel(0) and palladium(0) (equation 13 and Table 1). The reaction proceeds regioselectively to give (32) or (33) depending on both the alkene stmcture and catalytic system. Reactions catalyzed by phos-phine-palladium(0) complexes afford only products of the type (32), via selective cleavage of the C(2)— C(3)bondof(26). 

In the field of olefin carboxylation, stoichiometric reactions have been described to occur between non-activated alkenes, CO2 and an electron-rich transition-metal complexes, such as Ni(0) [3], Ti(II) [4] or Fe(0) [5]. A Pd-catalyzed CO2 fixation occurs into methylenecyclopropane derivatives affording lactones [6]. The reaction of carbon dioxide with ethylene is difficult and its carboxylation to propionic acid, catalyzed by Rh derivatives [7], needs drastic experimental conditions. 

Asymmetric transfer hydrogenation with a chiral ruthenium complex is an alternative option for preparation of substituted phenethyl alcohols, which are important building blocks for the agricultural fungicide, (S)-MA20565 [47]. In the enantioselective synthesis of antidepressant sertraline (50), different chiral secondary alcohols have been proposed as pivotal intermediates (Scheme 14). Reduction of the keto ester 46 catdyzed by oxazaborolidine 45 provides chiral intermediate 47 in 90% ee [48]. Alternatively, reductive fragmentation of C2-symmetric oxa-tricyclic alkene 48 with DIBAL catalyzed by a BINAP-Ni complex generates a novel intermediate 49 in 88 % yield with 91% ee [49]. 

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