RESEARCH
Over several decades, numerous companies
all over the world, including BASF, Dupont,
Shell, Dow, Kuraray, and Sinopec, investigated
the prospect of accessing adipate esters via
butadiene dicarbonylation. However, despite
extensive explorations, no such industrially
viable transformation was developed (23–38).
Some pilot tests were implemented (23–36),
but those processes all involved multistep re-
actions with insufficient selectivity (~60 to
80%) for the desired linear diester.
Here, we present a palladium-catalyzed dicar-
bonylation of 1,3-butadiene that provides dialkyl
adipates in ≥95% yield and ≥97% selectivity.
Key to success was the ligand design. Recently,
we developed bidentate phosphine ligands
for palladium-catalyzed alkoxycarbonylation
reactions in which basic pyridyl substituents
on phosphorus proved essential for high ac-
tivity (39). On the basis of that work and our
long-standing interest in carbonylation reac-
tions (40), we proceeded to investigate the di-
carbonylation reaction of 1,3-butadiene with
butanol as a model for the direct synthesis of
adipate diesters.
ORGANIC CHEMISTRY
Direct synthesis of adipic acid esters via palladium-
catalyzed carbonylation of 1,3-dienes
Ji Yang1, Jiawang Liu1, Helfried Neumann1, Robert Franke2,3, Ralf Jackstell1, Matthias Beller1*
The direct carbonylation of 1,3-butadiene offers the potential for a more cost-efficient and
environmentally benign route to industrially important adipic acid derivatives. However, owing to
the complex reaction network of regioisomeric carbonylation and isomerization pathways, a
selective practical catalyst for this process has thus far proven elusive. Here, we report the design
of a pyridyl-substituted bidentate phosphine ligand (HeMaRaphos) that, upon coordination to
palladium, catalyzes adipate diester formation from 1,3-butadiene, carbon monoxide, and butanol
with 97% selectivity and 100% atom-economy under industrially viable and scalable conditions
(turnover number > 60,000). This catalyst system also affords access to a variety of other
di- and triesters from 1,2- and 1,3-dienes.
arbonylation reactions are among the
most important applications of indus-
trial catalysis (1–5): Using carbon mon-
oxide (CO) as a highly versatile C1
building block with olefins, more than
the building blocks of polyamides and poly-
esters currently produced on a multimillion–
metric ton scale (16, 17). More specifically,
adipate diesters are used for plasticizers, per-
fumes, lubricants, solvents, several active phar-
maceutical ingredients, and, with respect to
scale, most importantly for the production
of nylons. Now, the main industrial route to
produce adipate diesters involves oxidation of
a mixture of cyclohexanol and cyclohexanone
by an excess of nitric acid, followed by es-
terification with the corresponding alcohols
(18–20). This process requires special equip-
ment owing to the acid’s corrosiveness and
produces stoichiometric amounts of nitrous
oxide (N2O) (21), which is a major scavenger of
stratospheric ozone and has nearly 300 times
the atmospheric heat-trapping capacity of
CO2 (22).
C
10 million metric tons of various carbonyl
compounds (aldehydes, acids, and esters) are
produced annually for numerous consumer
products. CO is a central intermediate in the
chemical industry that can be easily produced
either from fossil-based resources (coal or
gas) or from renewables (CO2 or biowaste).
Despite the initial discovery of homogeneous-
ly catalyzed carbonylation processes nearly
80 years ago (6–15), several unattained objec-
tives remain, perhaps most saliently the direct
dicarbonylation of 1,3-dienes. This reaction
would enable more environmentally benign,
atom-economical production of adipate esters,
As shown in Fig. 1, there are multiple chal-
lenges associated with this catalytic process:
(i) The catalyst must promote two different
carbonylation reactions on the diene substrate
(which could not be achieved previously); (ii)
the linear dicarbonylation product must be
1Leibniz-Institut für Katalyse e.V. an der Universität Rostock,
Albert-Einstein Str. 29a, D-18059 Rostock, Germany. 2Evonik
Performance Materials GmbH, Paul-Baumann-Str. 1, 45772
Marl, Germany. 3Theoretical Chemistry, Ruhr-University
Bochum, 44780 Bochum, Germany.
*Corresponding author. Email: matthias.beller@catalysis.de
Fig. 1. Reaction network involved in synthesis of adipates from 1,3-butadienes. The green outlines indicate the starting materials (1,3-butadiene, carbon
monoxide, and alcohol) and desired product adipic diester.
Yang et al., Science 366, 1514–1517 (2019)
20 December 2019
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