Palladium‐Based Telomerization of 1,3‐Butadiene with Glycerol Using Methoxy‐Functionalized Triphenylphosphine Ligands

Abstract

Glycerol is considered a potential renewable building block for the synthesis of existing as well as new chemicals. A promising route is the telomerization of 1,3-butadiene with glycerol leading to C8 chain ethers of glycerol with applications in, for example, surfactant chemistry. Recently, we reported a new set of palladium-based homogeneous catalytic systems for the telomerization of 1,3-butadiene with glycerol and found that palladium complexes bearing methoxy-functionalized triphenylphosphine ligands are highly active catalysts capable of converting crude glycerol without any significant loss of activity. Herein, we present a detailed account of these investigations by reporting on the influence of the butadiene/glycerol ratio, temperature, and reaction time on product selectivity and activity allowing further optimization of catalyst performance. Maximum activity and yield were reached for high 1,3-butadiene/glycerol ratios at a temperature of 90 degrees C, whereas the selectivity for mono- and diethers of glycerol could be optimized by combining high reaction temperatures and short reaction times with low butadiene/glycerol ratios. Variation of the PdII metal precursors and the metal/ligand ratio showed that palladium precursors with halogen ligands gave unsatisfying results, in contrast to precursors with weakly coordinated ligands such as [Pd(OAc)2] and [Pd(acac)2]. [Pd(dba)2], the only Pd0 precursor tested, gave the best results in terms of activity, which illustrates the importance of the ability to form a Pd0 species in the catalytic cycle. Finally, base addition resulted in a shortening of the reaction time and most likely facilitates the formation of a Pd0 species. Based on these results, we were able to realize the first attempts towards a rational ligand design aimed at a high selectivity for mono- and diether formation.

Improved Utilization of Crude Glycerol By-Product from Biodiesel Production

“…Another method of crude glycerol utilization is telomerization with 1,3-butadiene to form C 8 chain ethers, which have a wide range of applications such as useful building blocks for commercially valuable products such as detergents and surfactants (Behr et al 2009). Most recently, direct telomerization of pure as well as crude glycerol with 1,3-butadiene carried out over palladium complexes as catalysts was reported (Palkovits et al, 2008a(Palkovits et al, , 2008b.…”

Palladium‐Catalysed Telomerisation of Isoprene with Glycerol and Polyethylene Glycol: A Facile Route to New Terpene Derivatives

“…Our attention was drawn by the elegant experiments of Palkovits et al, who showed that crude glycerol can be telomerised with 1,3-butadiene in a biphasic system, in the presence of Pd-phosphine complexes. [7,8] We were interested in adapting this approach to the less active but more lucrative isoprene, the telomerisation of which would yield terpene derivatives with various possible applications in the cosmetics and detergents sectors. [9] Notably, there are only a few examples of isoprene telomerisation.…”

Pd-Catalyzed Telomerization of 1,3-Dienes with Multifunctional Renewable Substrates: Versatile Routes for the Valorization of Biomass-Derived Platform Molecules

“…The same group later reported a more extensive study on the Pd/TOMPP system in which the effect of the metal precursor, addition of base, butadiene/glycerol ratio as well as the ligand/metal ratio were investigated [33]. Commonly used palladium sources such as Pd(acac) 2 and Pd(OAc) 2 both worked equally well; the use of the palladium(0) complex Pd(dba) 2 resulted in a higher activity, illustrating the fact that the catalytic cycle starts with a Pd(0) species and the requirement for the Pd(II) salts to be reduced before they can enter the cycle.…”

“…At very low catalyst concentrations (0.002 mol%), PPh 3 outperformed all other ligands tested with a conversion of 58% and a TON of 30,500. Palkovits et al assessed the performance of different phosphines in the transformation of bulky nucleophiles such as glycerol to find the tris(o-methoxyphenyl)phosphine (TOMPP) ligand to be very efficient [32,33]. A recent patent awarded to Dow describes a number of ligands related to TOMPP, of which bis(2-methoxyphenyl)(4-(trifluoromethyl)phenyl)phosphine (L1) was found to be the most active in the telomerization of 1,3-butadiene with methanol [34].…”