Butadiene palladium complexes

Next, the effect of ligand of palladium complex on the reaction of butadiene was studied. Only vinylcyclohexene (4) was obtained by the reaction of butadiene at 90°C using bis(7r-allyl)palladium (13) and tri-chlorophosphine (1 1). 

After that, studies on the palladium-catalyzed reactions of conjugated dienes attracted little attention. They have only been reexamined since the late 1960 s. The scope of the reaction of butadiene catalyzed by palladium complexes has gradually been established. The catalysis by palladium is different from those of other transition metals. Although palladium is located below nickel in the periodic table, the catalytic... 

It is apparent from mechanistic considerations that an active species in the palladium-catalyzed dimerization of butadiene is a zero-valent palladium complex, which forms bis-ir-allylic complex 20. 

The main path of the palladium-catalyzed reaction of butadiene is the dimerization. However, the trimerization to form /j-1, 3,6,10-dodeca-tetraene takes place with certain palladium complexes in the absence of a phosphine ligand. Medema and van Helden observed, while studying the insertion reaction of butadiene to 7r-allylpalladium chloride and acetate (32, 37), that the reaction of butadiene in benzene solution at 50°C using 7r-allylpalladium acetate as a catalyst yielded w-1,3,6,10-dodecatetraene (27) with a selectivity of 79% at a conversion of 30% based on butadiene in 22 hours. 

Octatriene reacts further with butadiene in acetic acid by using 7r-allylic palladium complex as catalyst to give a mixture of acyioxydo-decatrienes (54). 

Hydrosilylation of butadiene using palladium complexes supported on inorganic materials such as silica and alumina has been carried out (77, 72) however, the supported catalyst is not stable and it is difficult to compare with the soluble catalysts. 

The carbonylation was explained by the following mechanism. Formation of dimeric 7r-allylic complex 20 from two moles of butadiene and the halide-free palladium species is followed by carbon monoxide insertion at the allylic position to give an acyl palladium complex which then collapses to give 3,8-nonadienoate by the attack of alcohol with regeneration of the zero-valent palladium phosphine complex. When halide ion is coordinated to palladium, the formation of the above dimeric 7r-allylic complex 20 is not possible, and only monomeric 7r-allylic complex 74 is formed. Carbon monoxide insertion then gives 3-pentenoate (72). 

Unlike nickel Catalysts, palladium complexes do not catalyze the homo-cyclization reaction to give CDT or COD. The difference seems to be due to a different degree of hydride shift and atomic volume. With palladium catalysts, the hydride shift is easier, and hence linear oligomers are formed. The characteristic reaction catalyzed by palladium is the cocyclization of two moles of butadiene with one-hetero atom double bonds such as C=N and C=0 bonds to give six-membered rings with two vinyl groups (19) ... 

Cross-conjugated trienes have attracted interest in polymer chemistry and theoretical chemistry as well as in synthetic chemistry.11 Although a palladium complex catalyzed 1,2-propadiene dimerization in the presence of water or an amine produced hydroxylated or aminated 2,3-dimethyl-2,3-butadiene,12 the method was not applied to the synthesis of cross-conjugated trienes. Another interesting feature... 

A catalytic asymmetric [4+2]-cydoaddition of a vinylallene with butadiene has been achieved successfully, in which a palladium complex modified by a ferrocene-derived chiral monophosphine ligand proved to be a superior catalyst transferring chirality to the product (Scheme 16.80) [90],... 

Ceric ammonium nitrate promoted oxidative addition of silyl enol ethers to 1,3-butadiene affords 1 1 mixtures of 4-(/J-oxoalkyl)-substituted 3-nitroxy-l-butene and l-nitroxy-2-butene27. Palladium(0)-catalyzed alkylation of the nitroxy isomeric mixture takes place through a common ij3 palladium complex which undergoes nucleophilic attack almost exclusively at the less substituted allylic carbon. Thus, oxidative addition of the silyl enol ether of 1-indanone to 1,3-butadiene followed by palladium-catalyzed substitution with sodium dimethyl malonate afforded 42% of a 19 1 mixture of methyl ( )-2-(methoxycarbonyl)-6-(l-oxo-2-indanyl)-4-hexenoate (5) and methyl 2-(methoxycarbonyl)-4-(l-oxo-2-indanyl)-3-vinylbutanoate (6), respectively (equation 12). 

The strong acidity of the proton at the C2 position of a [AMIM] ion has been well recognized 183). This cation can react with palladium complexes to form inactive l,3-dialkylimidazol-2-ylidene palladium complexes 200), as confirmed in a study of the conventional Pd(OAc)2/PPh3/base catalyst in ionic liquids for the telomerization of butadiene with methanol at 85°C 201). 

An interesting hydrosilylation reaction catalyzed by supported palladium complexes occurs between trimethylsilanol and butadiene ... 

Palladium complexes generated from the sulfonated ligand 5 (Table 2 R=Me, n=0,l,2) were also used to catalyse the telomerization of 1,3-butadiene with water108 and from the aminophosphines 83 (Table 5 R=Ph R =H,Me R"=Me,iPr n=2,3) with MeOH to give l-methoxy-2,7-octadiene in selectivities up to 78% at conversions ranging from 52 to 80%.232 Pd/83 (R=Ph R =H,Me R"=Me,iPr n=2,3) catalysts are more active but less selective in the latter reaction compared to their tppts counterparts.232 9... 

The procedure described by Kharasch4 for the preparation of complexes of palladium and olefins containing a single double bond has been extended to the preparation of the l,4-butadiene-palladium(II) chloride complex in the following procedure. 

Abstract The dimerization of 1,3-dienes (e.g. butadiene) with the addition of a protic nucleophile (e.g. methanol) yields 2,7-octadienyl ethers in the so-called telomerization reaction. This reaction is most efficiently catalyzed by homogeneous palladium complexes. The field has experienced a renaissance in recent years as many of the platform molecules that can be renewably obtained from biomass are well-suited to act as multifunctional nucleophiles in this reaction. In addition, the process adheres to many of the principles of green chemistry, given that the reaction is 100% atom efficient and produces little waste. The telomerization reaction thus provides a versatile route for the production of valuable bulk and specialty chemicals that are (at least partly) green and renewable. The use of various multifunctional substrates that can be obtained from biomass is covered in this review, as well as mechanistic aspects of the telomerization reaction. 

Takahashi S, Shibano T, Hagihara N (1967) Dimerization of butadiene by palladium complex catalysts. Tetrahedron Lett 2451-2453... 

Tsuji J (1973) Addition reaction of butadiene catalyzed by palladium complexes. Acc Chem Res 6 8-15... 

Dzhemilev UM, Kunakova RV, Baibulatova NZ, Tolstikov GA, Panasenko AA (1980) Telomerization of polyatomic alcohols with butadiene, catalyzed by low-valent palladium complexes. Zh Org Khim 16 1157-1161... 

Sasaki Y, Inoue Y, Hashimoto H (1976) Reaction of carbon dioxide with butadiene catalysed by palladium complexes. Synthesis of 2-ethylidenehept-5-en-4-olide. J Chem Soc, Chem Commun 605-606... 

Dzhemilev UM, Kunakova RV, Sidorova VV (1987) Joint catalytic activation of C02 and NH2 in reaction with butadiene under the action of palladium complexes. Russ Chem Bull 36 362-364... 

Less attention has been paid to the use of amines as nucleophiles in the telomerization reaction. A single report from Nolan and co-workers [233] has shown that well-defined cationic palladium complexes are efficient catalysts in the telomerization of butadiene with amines under mild conditions (Table 10). In the case of primary amines, the concentration of the reactants and their steric hinderance dictates the formation of a mono- or double-alkylated product. 

In the presence of HX = H02CR, HOR, HNR2, or a C—H acidic compound, palladium complexes catalyze the telomerization of butadiene, a selective route to 2,7-octadienyl derivatives ... 

Since such catalytic cycles involve transformations of organic species at a metal centre, a first step must be the formation of an organometallic. These can be formed by a direct reaction in which an organic reactant replaces a solvent or ligand molecule in the coordination sphere of a metal complex. For example, the ethylene-palladium(II) complex Pd(ri -C2H4)Cl2 2 can be formed by the direct reaction of PdCl2 with ethylene (Equation 1), and the butadiene-iron complex is also formed directly by replacement of two CO s on Fe (Equation 2). 

Musco has also investigated the dimerization of butadiene. He found that COj enhances the catalytic effect of tertiary phosphine-palladium complexes in the syntheses of 1,3, 7-octatriene and in the subsequent isomerization to 2, 4, 6-octauiene 1299]. 

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