Palladium-catalyzed Telomerization Research Articles

Sustainable Copolymer Synthesis from Carbon Dioxide and Butadiene.

Carbon dioxide (CO2) has long been recognized as an ideal C1 feedstock comonomer for producing sustainable materials because it is renewable, abundant, and cost-effective. However, activating CO2 presents a significant challenge because it is highly oxidized and stable. A CO2/butadiene-derived δ-valerolactone (EVP), generated via palladium-catalyzed telomerization between CO2 and butadiene, has emerged as an attractive intermediate for producing sustainable copolymers from CO2 and butadiene. Owing to the presence of two active carbon-carbon double bonds and a lactone unit, EVP serves as a versatile intermediate for creating sustainable copolymers with a CO2 content of up to 29 wt % (33 mol %). In this Review, advances in the synthesis of copolymers from CO2 and butadiene with divergent structures through various polymerization protocols have been summarized. Achievements made in homo- and copolymerization of EVP or its derivatives are comprehensively reviewed, while the postmodification of the obtained copolymers to access new polymers are also discussed. Meanwhile, potential applications of the obtained copolymers are also discussed. The literature references were sorted into sections based on polymerization strategies and mechanisms, facilitating readers in gaining a comprehensive view of the present chemistry landscape and inspiring innovative approaches to synthesizing novel CO2-derived copolymers.

Regioselectivity Control in Pd-Catalyzed Telomerization of Isoprene Enabled by Solvent and Ligand Selection

Controlling the selectivity in palladium-catalyzed telomerization of nonsymmetric dienes represents a formidable challenge since up to 12 isomers can be obtained, and a general method for selective synthesis is still lacking. We select isoprene (2-methylbutadiene) as a representative and relevant example of a nonsymmetric diene. A combined experimental–computational study on a large set of phosphine-modified palladium catalysts and reaction conditions aiming to understand the factors governing the selectivity shows that it can be controlled by selecting the protic solvent pKa and by the ligand. Atomistic and kinetic simulations reveal that the solvent switches the selectivity-determining step as a function of pKa from C–C oxidative coupling at low pKa values (preference for telomer head-to-head) to protonation at high pKa values (preference for telomer tail-to-tail). The selectivity toward tail-to-head telomer can be directed in moderately acidic solvents by selection of the appropriate ligand, which exerts steric control of the protonation step. Thus, using Et2NH as a nucleophile, it was possible to synthesize 3 of the 4 main isomers in very high yields and selectivities and to provide a complete mechanistic picture of Pd-catalyzed telomerization of nonsymmetric dienes.

Palladium-Catalyzed Functionalization of Kraft Lignin: Ether Linkages through the Telomerization Reaction.

Kraft lignin was efficiently functionalized with octadienyl ether linkages through the palladium-catalyzed telomerization of 1,3-butadiene. Comparison with molecular model substrates assessed the grafting of phenols and alcohols and an optimization study led to up to 69 % conversion of the total number of hydroxyl groups present in lignin. This catalytic study evidenced the partial oxidation of triphenylphosphine into triphenylphosphine oxide and triphenylphosphine sulfide by contaminants present in the industrial grade kraft lignin. The telomerised lignin is a malleable material and a preliminary study of the thermal properties showed a decrease in the glass transition in comparison with the starting material.

Preparation of CO₂/diene copolymers: advancing carbon dioxide based materials.

CO2-based materials: Metastable CO2/diene-based lactones, which were prepared by the palladium-catalyzed telomerization of CO2 and dienes, easily undergo aerobic radical homo-polymerization to give novel CO2-rich polymers. This two-step reaction set-up expands the potential applications of CO2-based copolymers by adding innovative compositions, structures, and properties.

Preparation and application of air-stable P, N-bidentate ligands for the selective synthesis of δ-lactone via the palladium-catalyzed telomerization of 1,3-butadiene with carbon dioxide

Air-stable P, N-bidentate ligands L1– L7 with cyclic secondary amine moieties linked to the benzene rings of triphenylphosphine were designed and prepared. The chelating coordination mode of the P, N-bidentate ligands to the Pd(II) center was confirmed by determining the X-ray structures of the Pd(II) complexes C1 and C2 derived from ligands L1 and L2, respectively. The ligands were used for the selective synthesis of δ-lactone through the palladium (Pd)-catalyzed telomerization of 1,3-butadiene with carbon dioxide. The highest yield (60% with 79% selectivity) was observed using the Pd 2(dba) 3/4-(2-(diphenylphosphino)phenyl)morpholine ( L2) catalyst system.

Large P−P Distance Diphosphines and Their Monophosphine Analogues as Ligands in the Palladium-Catalyzed Telomerization of 1,3-Butadiene and Methanol

The potential of diphosphines based on a dibenzodioxocin or benzofurobenzofuran backbone possessing large P−P distances was studied for the selective telomerization of 1,3-butadiene with methanol under commercially relevant process conditions to obtain 1-methoxyocta-2,7-diene (1-MOD). They were found to act as monophosphines. New bulky monophosphine analogues of the same backbone and ferrocene were also evaluated. Several ligands showed improved selectivity and yield compared to the benchmark ligand PPh3 and monoxantphos. Especially 1,6-bis(diphenylphosphino)-5a,10b-dihydro-5a,10b-dimethyl-3,8-dimethylbenzofuro[3,2-b]benzofuran (3) and, 2,10-di-tert-butyl-4-diphenylphosphino-6,12-methano-12H-dibenzo[2,1-d:1′,2′′-g][1,3]dioxocin (7), a diphosphine and a monophosphine, respectively, stand out as excellent ligands in terms of yield, selectivity, and stability.

Heterogeneous palladium-catalyzed telomerization of myrcene with glycerol derivatives in supercritical carbon dioxide: a facile route to new building blocks

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Efficient Telomerization of Butadiene with Starch in Water: The Role of the Surfactant

The synthesis of hydrophobic starch was performed via palladium-catalyzed telomerization of butadiene with native starch. This reaction is efficiently performed in water in the presence of neutral or cationic surfactant with high HLB. After optimization of the reaction conditions, TOF up to 446 was achieved.

Mechanistic study of palladium-catalyzed telomerization of 1,3-butadiene with methanol

The Pd-catalyzed telomerization in the presence of phosphine and carbene ligands has been computed. It is shown that the C-C coupling of the less stable complex A with one trans- and one cis-butadiene in syn orientation forms the most stable intermediate B and is favorable both kinetically and thermodynamically. Protonation of B leads to equilibrium of the two most stable isomers of intermediate C. The overall regioselectivity is favored thermodynamically.

A Practical Palladium-Catalyzed Telomerization for the Synthesis of Functionalized Alcohols

The synthesis of octadienyl-substituted alcohols via palladium-catalyzed telomerization is described. 2-N-Methylaminoethanol, ethylene glycol, and 1,2-propylenediol react smoothly with 1,3-butadiene to give valuable intermediates for speciality polymers in high selectivity and quantitative yield on multi-100 g-scale.

Telomerization and dimerization of isoprene by in situ generated palladium–carbene catalysts

The palladium-catalyzed telomerization of isoprene with methanol and dimerization of isoprene have been studied in presence of in situ generated palladium–carbene catalysts. Unprecedented catalyst productivity has been observed for these two reactions. A selectivity switch from the telomer to the dimer product occurred by using different substituted carbene ligands. Among the imidazolium salts tested 1,3-dimesitylimidazolium mesylate ( 1), 1,3-dimesityl-4,5-dihydroimidazolium chloride ( 3) gave the best yields for telomerization reaction whereas 1,3-bis-(2,6-diisopropylphenyl)-4,5-dihydroimidazolium tetrafluoroborate ( 5) and 1,3-bis-(2,6-diisopropylphenyl)-4,5-dimethyl-4,5-dihydroimidazolium chloride ( 9) form dimers in high yield and good selectivity.

Neutral pentosides surfactants issued from the butadiene telomerization with pentoses: preparation and amphiphilic properties

Interfacial properties of octadienyl pentosides prepared by the palladium-catalyzed telomerization of butadiene with free pentoses have been evaluated and compared to those of mixtures issued from the autoclaving process.

2-Pyridyl-2-phospholenes: New P,N ligands for the palladium-catalyzed isoprene telomerization

2-(2-Pyridyl)-2-phospholenes are efficient ligands for the palladium-catalyzed telomerization of isoprene with diethylamine. Good selectivities for the tail-to-head or tail-to-tail aminoterpenes are achieved on optimization of the ligand substituents and of the reaction conditions, such as the nature of the catalyst precursor and of the solvent. Moreover, excellent catalytic activities are achieved on photochemical activation or addition of acidic co-catalysts.

Synthesis of C 8 alkyl glycosides via palladium-catalyzed telomerization of butadiene with O-benzylated aldoses

Conditions of the butadiene telomerization with benzylated aldoses with a free anomeric hydroxyl, which efficiently furnish the corresponding octadienyl compounds have been determined. Deprotection and hydrogenation of the telomers over Pd/C led to the octyl glycosides.

Effects of the reactants concentration in the butadiene telomerization with d-xylose and parallel influence of triethylamine as additive

The efficiency and the selectivity of the palladium-catalyzed telomerization of butadiene with d-xylose in DMF were strongly dependent on the presence of triethylamine as additive for low sugar concentrations. The amine influence, which would mainly be due to its both basic and coordinating properties, disappeared at high sugar concentrations. The selectivity towards the monografting could reach 98% at 50% sugar conversion (with 82% of linear isomers) and could be maintained at 71% at 96% conversion (with a similar ratio of linear isomers).

The Importance of Imidazolium Substituents in the Use of Imidazolium-Based Room-Temperature Ionic Liquids as Solvents for Palladium-Catalyzed Telomerization of Butadiene with Methanol

Room-temperature ionic liquids are used as cosolvents in the palladium-catalyzed telomerization of butadiene with methanol. The basic catalyst is palladium(II) acetate with either triphenylphosphin...

Palladium-catalyzed telomerization of butadiene with ethylene glycol in liquid single phase and biphasic systems: control of selectivity and catalyst recycling

Abstract The palladium-catalyzed telomerization of 1,3-butadiene (Bu) with ethylene gylcol (EG) has been studied in liquid single phase and aqueous biphasic systems. All important parameters have been examined, including temperature, catalyst system, catalyst concentration, Bu/EG ratio, P/Pd ratio, solvent and reaction time. In homogeneous phase mixtures of 2-(2,7-octadienyloxy)ethanol ( 1a ) and 2-(1-ethenyl-5-hexenyloxy)ethanol ( 1b ) were formed in yields up to 60%, but also ditelomers ( 2 ) and butadiene dimers ( 3 ) were produced in significant amounts. In aqueous biphasic systems, however, using a palladium catalyst with the triphenylphosphinetrisulfonate (TPPTS) ligand, the monotelomers 1a and 1b were obtained in 80% yield with more than 95% selectivity. A mechanism is proposed explaining the observed differences in selectivity. The aqueous catalyst phase could be recycled six times resulting only in a slight decrease of activity. The products 1a and 1b were hydrogenated in quantitative yield to the corresponding saturated compounds 2-octyloxyethanol ( 6a ) and 2-(1-ethyl-hexyloxy)ethanol ( 6b ) using a Pd/Al 2 O 3 catalyst under mild conditions. The products can be used for a variety of applications like plasticizers, cosmetics and solvents.

Palladium-Catalyzed Telomerization of Butadiene with Starch

In order to modify the hydrophilic properties of native starch for its incorporation in polymers, the telomerization of butadiene with native starch was investigated. Low to moderate degrees of substitution (DS=0.04–0.52) were obtained depending upon experimental conditions, particularly, reaction time, temperature and solvent. With 0.3‰ water-soluble palladium catalyst (Pd/TPPTS), the reaction occurred in i-PrOH/NaOH 0.1 N solvent mixture even at 50 °C and after 3 h reaction the DS reached 0.08, a value suitable for the application.

Efficient telomerization of 1,3-butadiene with alcohols in the presence of in situ generated palladium(0)carbene complexes

The palladium-catalyzed telomerization of 1,3-butadiene with alcohols has been studied in presence of palladium and imidazolium salts, which form in situ carbene ligands. Among the different imidazolium salts tested 1,3-dimesitylimidazolium chloride ( 7), 1,3-bis(ferrocenylmethyl)benzimidazolium tetraphenylborate ( 12) and 1,3-bis(2-ferrocenylethyl)benzimidazolium bromide ( 13) gave the best yields of the desired octadienyl ethers. Significantly improved regioselectivities for the linear octadienylethers are obtained in the reaction of 1,3-butadiene and methanol compared to the previously optimized palladium/triphenylphosphine catalyst. Using n-butanol and iso-propanol the palladium carbene catalysts lead to a considerable increase in the corresponding telomerization products compared to standard palladium/triphenylphosphine catalysts.

Palladium-Catalyzed Reactions for the Synthesis of Fine Chemicals, 16 – Highly Efficient Palladium-Catalyzed Telomerization of Butadiene with Methanol

Palladium-Catalyzed Reactions for the Synthesis of Fine Chemicals, 16 – Highly Efficient Palladium-Catalyzed Telomerization of Butadiene with Methanol