Butadiene dimerization-carbonylation

This test method provides for the determination of butadiene-1,3 purity and impurities such as propane, propylene, isobutane, n-butane, butene-1, isobutylene, propadiene, fra/i5-butene-2, cu-butene-2, butadiene-1,2, pentadiene-1,4, and, methyl, dimethyl, ethyl, and vinyl acetylene in polymerization grade buta ene by gas chromatography. Impurities including butadiene dimer, carbonyls, inhibitor, and residue are measured by appropriate ASTM procedures and the results used to normalize the component distribution obtained by chromatography. 

Carbonyiation of butadiene gives two different products depending on the catalytic species. When PdCl is used in ethanol, ethyl 3-pentenoate (91) is obtained[87,88]. Further carbonyiation of 3-pentenoate catalyzed by cobalt carbonyl affords adipate 92[89], 3-Pentenoate is also obtained in the presence of acid. On the other hand, with catalysis by Pd(OAc)2 and Ph3P, methyl 3,8-nonadienoate (93) is obtained by dimerization-carbonylation[90,91]. The presence of chloride ion firmly attached to Pd makes the difference. The reaction is slow, and higher catalytic activity was observed by using Pd(OAc) , (/-Pr) ,P, and maleic anhydride[92]. Carbonyiation of isoprcne with either PdCi or Pd(OAc)2 and Ph,P gives only the 4-methyl-3-pentenoate 94[93]. 

Simple carbonylation and dimerization-carbonylation of butadiene take place in alcohol depending on the catalytic species of palladium. When PdCl2 is used as a catalyst with or without PPh3, 3-pentenoate (72) is the sole product (74, 75). On the other hand, when Pd(OAc)2 is used with PPh3, the dimerization-carbonylation takes place to give 3,8-nona-dienoate (73) (76, 77). 

Because of its potential application to the synthesis of estersfor lubricating oils, the dimerization-carbonylation of butadiene has received special attention. Basic phosphines such as PBun3 and weakly basic tertiary amine solvents (quinoline, N, N-diethylaniline) were found to improve both the stability and activity of the catalyst system.S3° In a further report in which PPr 3 was used as phosphorus ligand it was found that the addition of maleic anhydride caused a marked increase in the catalytic activity. It was believed that through coordination it stabilized the palladium(O) complexes formed against precipitation as metal.s 1... 

The dimerization of butadiene has been studied principally in the liquid phase. Most of the data have been obtained on the reaction which is brought about by photosensitization to the lowest triplet state of butadiene with carbonyl compounds as sensitizers. The solvent was liquid butadiene. The three isomers that are formed under these conditions are cfs-divinylcyclobutane (1), irans-divinylcyclobutane (2), and 4-vinylcyclohexene (3). 

The carbonylation of butadiene, readily available from petroleum sources, yields a dicarbonylated adduct and dimer-carbonylated product, both desirable from a commercial standpoint. Palladium-catalyzed reactions yield monocarbonylated ... 

The reaction of 1,3-butadiene catalyzed by PdCE gives an alkyl 3-pentenoate (Eq. 50), whereas the Pd(OAc)2(PPh3)2-catalyzed reaction yields an alkyl 3,8-nonadienonate via a dimerization-carbonylation process (Eq. 51)." ... 

A novel route to azelaic acid is based on butadiene. Butadiene is dimerized to 1,5-cyclooctadiene, which is carbonylated to the monoester in the presence of an alcohol. Hydrolysis of this ester foUowed by a caustic cleavage step produces azelaic acid in both high yield and purity (56). 

Nickel(O) complexes are extremely effective for the dimerization and oligomerization of conjugated dienes [8,9]. Two molecules of 1,3-butadiene readily undergo oxidative cyclization with a Ni(0) metal to form bis-allylnickel species. Palladium(O) complexes also form bis-allylpalladium species of structural similarity (Scheme 2). The bis-allylpalladium complexes show amphiphilic reactivity and serve as an allyl cation equivalent in the presence of appropriate nucleophiles, and also serve as an allyl anion equivalent in the presence of appropriate electrophiles. Characteristically, the bis-allylnickel species is known to date only as a nucleophile toward carbonyl compounds (Eq. 1) [10,11],... 

The only Zr(0) carbonyl complex has been prepared by Wreford and co-workers. When ZrCl4 was treated with l,2-bis(dimethyl-phosphino)ethane (dmpe), and then subsequently reduced with sodium amalgam in the presence of 1,3-butadiene, the dmpe bridged dimer, [(t/-C4H6)2Zr(dmpe)]2(dmpe) (65), resulted (114). The brown crystalline dimer 65 was found to be in equilibrium with the 16-e- coordinatively unsaturated complex, (tj-C4H6)2Zr(dmpe) (66), and free dmpe. When toluene solutions of 65 were exposed to CO at —45°C, 1 equivalent of CO per equivalent of Zr was consumed and the CO adduct (r/-C4H6)2Zr-(dmpe)(CO) (67) precipitated as a yellow solid. If these mixtures were allowed to warm above -22°C under vacuum, the precipitate dissolved and the consumed CO evolved (114). Complex 67 could be isolated by... 

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). 

The carboxytelomerization, a variant to the usual telomerization, is the carbonylation-dimerization of butadiene, carbon monoxide and alcohols. 

Ni-organic chemistry of butadiene started in the early 1950 s when this substrate could be slowly dimerized to cis, cis-cycloocta-l,5-diene in relatively low yields ( 40%) by using so-called Reppe catalysts of the type L2Ni (CO)2. Carbonyl-free low-valent Ni-complexes and catalysts on the basis of Cr and Ti were more effective and also led to further ring-syntheses (Scheme 1-1)... 

Typically, little butadiene is dimerized to 4-vinylcyclohexene under actual reaction conditionsOO,31). The butadiene used in the process, however, can contain up to. 5 weight % Diels-Alder product, and at this level oxidative carbonylation can become a significant heavies forming reaction (Equation 9.). The major product from this reaction comes from l, -dicarbonylation of the 4-vinylcyclohexene exocyclic double bond. 

Butadiene is available commercially as a liquefied gas underpressure. The polymerization grade has a minimum purity of 99%, with acetylene as an impurity in the parts-per-million (ppm) range. Isobutene, 1-butene, butane and cis-l- and Zrc//7.s-2-butcnc have been detected in pure-grade butadiene (Miller, 1978). Typical specifications for butadiene are purity, > 99.5% inhibitor (/c/V-butylcatecliol). 50-150 ppm impurities (ppm max.) 1,2-butadiene, 20 propadiene, 10 total acetylenes, 20 dimers, 500 isoprene, 10 other C5 compounds, 500 sulfur, 5 peroxides (as H2O2), 5 ammonia, 5 water, 300 carbonyls, 10 nonvolatile residues, 0.05 wt% max. and oxygen in the gas phase, 0.10 vol% max. (Sun Wristers, 1992). Butadiene has been stabilized with hydroquinone, catechol and aliphatic mercaptans (lARC, 1986, 1992). 

The hydroesterification of dienes gave both the unsaturated monoesters and saturated diesters.524 In some cases, y-ketoesters were obtained and carbonylation of 1,5-cyclooctadiene in absence of alcohol gave a ketone.525 [PdI2(PBu3)2] was used as catalyst. If the catalyst contained a halide anion, butadiene underwent normal hydroesterification. When halide-free catalysts were used, the reaction took a different course. Dimerization of the diene occurred to give the ester of 3,8-nonadienoic acid as the major product (equation 128).526-528... 

In the presence of iron carbonyl complexes 372), the dimerization of the butadiene can be substantially suppressed ... 

Polymerization was carried out in benzene in the presence of bis-(7r-allylnickel halides). The latter were prepared from nickel carbonyl and allyl halide (allyl bromide, crotyl chloride, bromide, or iodide etc.). The results of the polymerization runs are reported in Table I. The data indicate that all of the bis(7r-allylnickel halides) initiate by themselves the stereospecific butadiene polymerization yielding a polymer with 97-98% 1,4-units. The cis-l,4/trans-l,4 ratio depends on the halide in the dimeric r-allylnickel halide but not on the nature of allylic ligand. The case of bis(7r-crotylnickel halides) shows the effect of halide on microstructure, for whereas (C4H7NiCl)2 initiates cis- 1,4-polybutadiene formation, trans-1,4 polymers are produced by (C4H7NiI)2. The reactivity increase in the series Cl < Br < I. 

Although the early examples of the 4ir participation of heterodienes in [4 + 2] cycloaddition reactions describe their reactions widi electron-deficient aJkenes, e.g. the thermal dimerization of a,3 unsaturated carbonyl compounds, the introduction of one or more heteroatoms into the 1,3-butadiene framewoiic does convey electrophilic character to the heterodiene. Consequently, such systems may be expected to participate preferentially in LUMOdiene-controlled Diels-Alder reactions with electron-rich, strained, or simple alkene and alkyne dienophiles. The complementary substitution of the heterodiene with one or more electron-withdrawing substituents further lowers the heterodiene Elumo, accelerates the rate of heterodiene participation in the LUMOdioie-conn-olled Diels-Alder reaction, and enhances the observed regioselectivity of the [4 + 2] cycloaddition reaction. ... 

Since the disclosures that the thermal dimerizations of acrolein and methyl vinyl ketone provide the 3,4-dihydro-2//-pyrans (1, 2) derived from 4ir and 2Tt participation of the a,3-unsaturated carbonyl compound in a Diels-Alder reaction, an extensive series of related observations have been detailed. This work has been the subject of several comprehensive reviews - - including the Desimoni and Tacco-ni extensive tabular compilation of work through 1974. Consequently, the prior reviews should be consulted for thorough treatments of the mechanism, scope, and applications of the [4 + 2] cycloaddition reactions of a,3-unsaturated carbonyl compounds. The [4 + 2] cycloaddition reactions of 1-oxa-1,3-butadienes with their 4-it participation in the Diels-Alder reaction exhibit predictable regioselectivity with the preferential or exclusive formation of 2-substituted 3,4-dihydro-2W-pyrans (equation 1). The exceptions to the predicted regioselectivity that have been observed involve the poorly matched [4 + 2] cycloaddition reaction of an electron-deficient l-oxa-l,3-butadiene with an electron-deficient dienophile, e.g. methyl crotonate or methacrolein. - Rigorous or simplified theoretical treatments of the [4 + 2] cycloaddition reaction of 1-oxa-1,3-butadienes predict the preferential formation of 2-substituted 3,4-dihy-dro-2f/-pyrans and accommodate the preferred endo approach of the reactants in which the carbon-carbon bond formation is more advanced than carbon-oxygen bond formation, i.e. a concerted but nonsynchronous [4 + 2] cycloaddition reaction. ... 

A most important application of butadiene carbonylations is BASF s development of a three-stage process for the synthesis of adipic acid from the butadiene-containing C4 cut [1] (eqs. (4) and (5)). Cobalt is the catalyst metal of choice for this process. The reaction takes place in two steps the first stage, which involves a lower temperature (100-140 °C), uses a fairly high concentration of HCo(CO)4 and pyridine as catalyst system to ensure rapid carbonylation of butadiene to give methyl pent-3-enoate in 90 % selectivity, thus avoiding typical side reactions such as dimerization and oligomerization. 

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